Here's a short history of Pagan origins scholarship:

1835: Strauss shows Jesus stories are myths 
1850 - early 1900s: Mythicists discover or invent dying and rising God parallels 

Conservative Christians	Different/ First/ Independent/ God's magic/ etc.
Liberal Academics	assume historical background to New Testament, invent literary methods to sift for "historical Jesus"
Academics	explore individual parallels: magic, divine birth, heaven, hell, etc
Wild ass theories	interpret 1st century Christian records' failure to mention Galilean Jesus as evidence there was no Galilean Jesus. Jesus is entirely mythical.

New Testament as myth. David Friedrich Strauss 1835
We've seen that in 1835 Strauss' The Life of Jesus Critically Examined kicked open the door to the idea that the gospel stories about Jesus were not histories, but myths. This suggested a question: Where did the myths come from?

Direct copying -- late 1800s, early 1900s
The simple answer suggested itself in the mid and late 1800s, as archeologists discovered and, for the first time, translated ancient Assyro-Babylonian-Akkadian-Sumerian cuneiform texts. Turns out ancient Mesopotamian people told stories way similar to stories in our bible. Gods like our God, breathing life into first men and first women created from clay. Floods like our flood, all the way down to plot details like sending out birds from the ark, and God enjoying the smoke of the sacrifice Utnapishtim—and, centuries later, Noah—burned at an altar. And so on. You get the picture. Point by point, myth by myth, religious idea by religious idea, ancient Judaism fits neatly into the flow of ancient middle eastern culture.

OK, so it's obvious where the Jewish myths come from. How about the Jesus stories, the ones Strauss had convinced people were myths? The simple answer, the one that looked obvious to free thinkers at the time, was that like Judaism Jesus was also a knock-off copy of ancient pagan religions. Enthusiastic amateur and ernest but undisciplined professional scholars went searching for myths like the Jesus myth. And, they said, they found them. Point by point, fact by fact, they found dying and rising savior Gods, born on the 25 of December, of virgin mothers, with 12 disciples. Like that.

The truth is, it wasn't so simple. People got carried away. Sure, some of what the mythicist scholars found was sort of similar to Jesus. But other stuff wasn't. In the rush of discovery, excited scholars filled in gaps in the copycat mythicist theory with facts that weren't really there. Nowadays we remember Sir James Frazier as the professional scholar behind this copycat dying and rising god theory of Jesus. There were several others.

Later, well into in the 20th century, a German guy named Bultmann, and a French fellow named Loisy tossed away the copycat mythicists' un-factual factual details, and found enough similarities left over to write influential books going through the New Testament in excruciating (I choose this word carefully) detail, laying out (among other things) grand theories of a mythic Christ.

It takes about an hour sitting with Frazier, Bultmann, Loisy et pals to spot the trouble with their theories. No footnotes. They drone on page after page, claiming this, asserting that. The only thing missing is rigor. And, for most of their shtick, evidence.

Mid 20th century. Conservative counterpunch: different/ first / independent.
To counter the mythicists, believing Christians simply parried Pagan-Christian similarities with belief-friendly, myth-dismissing explanations that leave Christianity looking new and unique. The Jesus stories are different, came first, developed independently, etc.

In 1928 a christian journal published the Reverend Arthur Darby Nock's long article "refuting" the then popular idea that Jesus' myth derived from Pagan mystery religions: Early Gentile Christianity and Its Hellenistic Background. (details at Con: AD Nock.) Nock's analysis is not comprehensive or consistent; the mere pretence of refutation satisfied conservatives.

As it satisfies yet today. Believers still cite Rev. Nock's eighty year old magazine article as the definitive refutation of "outdated" pagan origins scholarship, and they build later re-refutations on his arguments. BM Metzger's essay Methodology in the Study of the Mystery Religions and Early Christianity (1968) repeats and extends Nock. Believers also cite Metzger's essay as definitive, though at just a few pages it is too short to be anything but a trivial critique, and its analysis is anyway transparently tendentious.

Facts are stubborn things. In spite of believers' definitive refutations, the notion that Christianity has Pagan origins remains popular. By the 1990s, and in a reprint in 2003, Christian popularist professor Ronald Nash's The Gospel and The Greeks was able not only to outdo Nock and Metzger's uncritical reasoning (Nash's trick is to dig deep enough to find some difference of detail between our stories and their myths), but also to ignore the last fifty years of modern scholarship, and adjust away unfavorable facts—seventy-five years after Nock, believing scholarship has simply forgotten the basic evidence.

The conservative Christian reply to the notion of a mythic Christ is generally breaks down to different/ first/ independent. The reply comes out in books and articles written by one believer for other believers. Everyone in the target audience picks up the magazine already believing the "refutation's" conclusion. Because no readers will argue with the conclusions, the refuting "scholar" doesn't have to be rigorous. And they never are. They all repeat silly reasoning, and move the facts around so they fit the preordained conclusion. [Details at Different / First / Independent / etc under the Borrowing tab.]

Mid 20th century, Liberal scholarship's "Historical Jesus"
It's not only conservative Christians whose beliefs are threatened by a mythic Jesus. Even squishy allegory-interpreting, essential-human-condition experiencing, sort-of-but-not-in-a-literal-way believers see that if their Jesus stories are just Pagan myths reheated, that pretty much cuts the New Testament off at ground level, and grinds away the stump. May as well read Aesop. Liberal academic scholarship isn't ready for that.

The fashion in modern academic NT scholarship is to work within a Grand Theory that assumes some sort of at least half-assed historical connection between the gospel sayings and the assumed founder of Christianity, Jesus. Several generations of associate professors have thrown their lives at nit picking "literary criticism" imagined to tease out the real "historical" Jesus.

The results of this grand theory are mixed. Some of it's fact-based conclusions are way cool, particularly stuff about which gospel writers copied which other gospel writers, and details about the now lost but reconstructable gospel sayings source called Q. But when it comes to finding the Historical Jesus, literary criticism has failed. Some scholars see a Jewish rabbi. Others see a nutter millenialist. Or a magician. Or a cynic philosopher. The list goes on and on. The reason literary criticism gives twenty Historical Jesoi and not one Historical Jesus is, literary criticism does not work.

Christian-Pagan similarities-wise, academic scholarships' answer is basically to ignore theories of meaningful Christian borrowing. Sure, there are peripheral cultural similarities. But associate professors know, because they assumed it, that the New Testament stories and quotations go back to a historical Jesus. Because of that there is no possibility of a fundamental connection between our stories and their myths.

Individual parallels
Some academics do break out and write books giving extended primary evidence of similarities between Christianity and Paganism. See below, Good Books for details

Wild ass theories
Of course in a short round up like this I've got to paint with a wide brush. In fact there are some academics who don't swallow the fashionable grand theory's assumption of a Historical Jesus. There are two basic alternate theories:

1) There was maybe a Historical Jesus, but our gospel stories about Him are not based entirely on a historical record of His life. The gospels were written later, by folks who filled in missing bits with theological "facts" that made the story come out the way their theology said it had to. I.e., they made it up.

For example, Professor MacDonald's Homeric Epic and the Gospel of Mark explains how the Gospel of Mark borrowed its structure and ideas from Homer's Iliad.

2) There was no Historical Jesus. Paul and the other first Christians believed in a mythic Jesus who fulfilled old Jewish prophecies; the gospels were written later by people who took the old myths literally and wrote the gospels stories to fill in details they figured must have happened. Sort of like how the 19th century mythicist scholars invented facts to fill in details they figured must have happened..

The famous advocates of theory 2 are are GA Wells and Earl Doherty.

The academic response to wild ass theories is to ignore, or snicker, rather than refute.

Enthusiastic amateurs write undisciplined books repeating the outdated direct copying theories of the 1800s. These folks generally recycle secondary sources going back to the imaginative 19th century mythicists. Smart people like you will snicker and ignore.

Drudgery Divine
On the Comparison of Early Christianities and the Religions of Late Antiquity (1994)
By Jonathan Smith

	A scholar's detailed review of the Pagan-Origins scholarship from the 15th century through the early 1990s.
	Details of why the "scholarly" conclusions on each side are agenda driven. For example, there's a nice refutation of AD Nock's linguistic argument.

But, because Professor Smith thinks obscure is clever, the writing is terrible. This book will not make sense until you've read A.D. Nock's Early Gentile Christianity and Its Hellenistic Background.

Here's a sample >>

Jesus, admits Professor Smith quoting the Christian-borrowing scholar Loisy, was a savior-God like Osiris, Attis and Mithras. He was a god who came to earth, died, and saves, etc. etc.

from which, opines Professor Smith,
"little of value can be learned." [!!]

Professor Smith is famous for his anti-borrowing agenda—which is why he's quoted a lot.

"[Jesus] was a savior-god, after the manner of Osiris, and Attis, a Mithra. Like them, he belonged by his origin to the celestial world; like them, he had made his appearance on the earth; like them, he had accomplished a work of universal redemption, efficacious and typical; like Adonis, Osiris, and Attis he ha died a violent death, and like them he had returned to life; like them, he ad prefigured in his lot that of the human beings who should take part in his worship, and commemorate his mystic enterprise; like them, he had predetermined, prepared, and assured the salvation of those who became partners in his passion." [Quoting A. Loisy, The Christian Mystery, in: The Hibbert Journal, 10(1911 - 12), 51]
Of which Smith says:
From such a parataxis of 'likeness', little of value can be learned.
[pages 42 - 43]

The Life of Jesus Critically Examined
first published 1835
by David Friedrich Strauss
translated by George Eliot

Ugarit and the Old Testament (1983)
by Peter Craigie
Professor of Religious Studies and Dean of Humanities at the University of Calgary, Alberta

A nice little (110 page) general-audience introduction to Ugarit (modern Ras Shamara in Syrian), where clay tablets discovered in 1929 revealed a pre-Israelite Semitic civilization with gods and myths similar to, but earlier than, Old Testament gods and myths.

If you can find it cheap, read this before you read Smith's Origins of Biblical Monotheism.

Like most books about Ugarit, this one is out of print but often available used at Amazon.com. It's not worth the ridiculously high price ($70 last I looked) they usually ask there. I got mine for $7 at ebay.

Early Gentile Christianity and Its Hellenistic Background
by Doctor of Divinity Arthur Darby Nock

	the leading non-borrowing scholar- apologist admits deep similarities between the Pagan mystery religions and Christianity.
	The canonical believers' reasons why each and every one of those similarities doesn't count.

First published in 1928 and reissued and updated in 1964, this is the canonical refutation of the late 19th and early 20th century scholarly claims that Christianity borrowed from Paganism.  This essay is widely cited as an authority, "Dr. Nock has refuted the German School. . .", and the arguments Nock developed here are the same ones believers use today.

The Eucharist ... is in line with contemporary mysteries, which purported to represent the sufferings and triumph of a god, in which his worshipers sympathized and shared....The Eucharist is a mystery, as mysteries were then understood, and Christianity, the heir of Judaism, has also an essential spiritual continuity with Hellenistic religion.
[pg 72]

Nock was also a committed Christian, a Doctor of Divinity who wasn't about to admit Christianity borrowed from Paganism, so for every similarity he comes up with a reason the similarity doesn't count.

The 1964 Harper Torchbook edition is expanded with Nock's later thoughts and arguments. 

It is out of print, but often available used through Amazon

The Gospel and the Greeks
by Ronald Nash

	A Christian philosophy professor's easy, readable, affordable roundup of the current state of the apologists' "refutation" of Christianity's Pagan origins.. The more you know, the less persuasive Professor Dr. Nash is.
	Eighty percent explanation of the mid-20th century scholarly dispute; twenty percent gentle kettle logical refutation. Good chapters explaining the monotheism of the Platonists and Stoics, the Mystery religions and the Gnostics.

Because he was a Christian writing for other Christians, Nash (who seems like a smart, likable fellow) was able to write an apologist genre book—one whose tendentious reasoning betrays no expectation of unfriendly critical analysis. His analysis was basically:

1. To ignore similar fundamental ideas (soul, heaven, salvation, godman), and to attack outdated mid-20th century Jesus as a myth-by-myth analogue theories,

2. To bring up differences between Pagan myths and Christian myths, and then apply the apologists' difference-proves-no-borrowing rule.

Available used at Amazon .com

A sourcebook of extended quotations from ancients, all dealing directly with the Pagan mystery religions.

Who you gonna trust?  The ancients. Believing scholars shade the facts in favor of the myth.  Non-believers exaggerate and make up facts and connections as a way to attack the church. 

So who are you going to trust?  That's up to you.  I trust the ancients—people alive back when Christianity began, and before. That's what this book is about.

This is a sourcebook, a collection of primary documents—excerpts from ancient authors who wrote about Pagan religion and early Christianity.  It's a great collection, with the original text of most of the standard ancient references to the pagan mystery religions.

This is a powerful book. You'll discover firsthand, right from the pens of the ancients themselves,  that Dionysus came to earth "incognito, disguised as a man"; that Pagan Gods died and were reborn with the meaning that "the God is saved, and we shall have salvation."; that pagans had initiation ceremonies seen as "a voluntary death", sacred meals shared with the God, ceremonial washing, Pagan miracles, a Godman who changed water into wine, and a Pagan version of the great flood.  And much more.  

An important book that no serious student will be without. Highly recommended.

.

Ancient Science and Dreams
Oneirology in Greco-Roman Antiquity
by Andrew Holowchak

	A readable scholarly survey of ancient ideas about dreams.
	The dream related ideas of Plato, Aristotle, Lucretius, Stoic philosophy, Artemidorus, Synesius.
	Dreams in ancient medicine. Hippocrates, Roman secular medicine, ancient religious incubation.
	A nice bibliography of ancient sources.

An excellent, readable, evidence based survey of the basic facts. Highly recommended.

Asclepius
Collection and Interpretation of the Testimonies
by Emma & Ludwig Edelstein

	This is the definitive scholarly work on the God Asclepius. You get two volumes in one book.
	Volume 1: 450 pages of primary source material: ancient literature, history, and inscriptions mentioning the God Asclepius.
	Volume 2: 260 pages describing and analyzing the evidence. The Hero, the God, Temple Medicine, Cult, Image, Temples.

Primary evidence assembled in the 1940s, still in print because no one since has done better.

Born Divine
The Births of Jesus & Other Sons of God
by Robert MIller

A glossy coffee table book full of beautiful pictures of Egyptian Gods taken from surviving papyruses, etc., and, who'd a thunk it, of lots of fun scholarly information about ancient Egyptian religion.

Surviving ancient texts, including Egyptian book of The Dead and the Pyramid Texts, etc. describe an afterlife of happiness for good people and torment for bad people, mediated by the great savior Gods Ra and Osiris.

The Egyptians had not one soul, but several—the ba, the ka, the shadow, the name—all of which survived death.

A well written, pretty, wonderful book, if you like this sort of thing.

.

Demonology of the Early Christian World
by Everett Ferguson

	Jesus and the demons, in the New Testament.
	Greek Views on demonology
	Jewish views on demonology
	Early Christian views on demonology

You can buy this book through Amazon, but I've never seen it there for less than $85. Ouch. See if your local library can get a copy from a university, through inter-libary loan.

Life After Death
A History of the AFterlife in Western Religion

by Alan Segal

	Primary ancient evidence—archaeology, inscriptions, and texts— detailing the overlap of magic with Greek religion
	Chapters include, among others: Incantations and Prayers for Salvation on Inscribed Greek Amulets Dreams and Divination in Magical Ritual Prayer in Magical and Religious Ritual Magic and Mystery in the Greek Magical Papyri

Poindexter heaven.

Martyrdom and Noble Death
Selected Texts from Graeco-Roman, Jewish and Christian Antiquity
by Jan van Henten and Friedrich Avamarie

Lousy with miracles Like chocolate chips in mama's cookies, miracles were a basic ingredient in ancient people's understanding of how the world works. Every bite—another miracle. The ancient world was lousy with miracles.

Don't believe me, believe the ancients. This excellent sourcebook gives hundreds of examples—250 pages—of ancient miracles recorded by the pens of ancients themselves.

You'll read short excerpts from ancient texts describing Pagan Gods who healed the sick (blindness, paralysis, lameness), raised the dead, exorcised demons, controlled nature, turned water into wine, walked on water, calmed storms, and more.

Well organized, easy to read. Highly recommended.

.

The Early Greek Concept of the Soul
by Jan Bremmer

The Riddle of Resurrection Dying and Rising Gods in the Ancient Near East
by Tryggve Mettinger

	An up to date scholarly review of the Dying and Rising God question. There really were Dying and Rising Gods.
	A look at 20th century scholarship about Dying and Rising Gods—the "scholarship" doesn't come out smelling good.

Ever since Jimmy Frazer wrote the Golden Bough more than a hundred years ago, pointing out that the ancient middle east was hopping with "dying and rising gods," people have argued if Jimmy had things straight.

Dr. Mettinger, of the Dept of Theology, Lund U. in Sweden, reviews the scholarship on the issue, through 2000.

That's less cool than you'd think for a couple reasons.
#1 The scholarship deals a lot on archaic gods like Baal, Melquart, Adonis, and there's not a lot of surviving info on them—so the issue often comes down to scholarly speculation, or scholarly spatting over cuneiform verb forms, as in (I am not making this up):

hklh. sh. lqs. ilm. tlhmn
ilm w tstn. tstnyn `d sbí
trt. `d. skr. yí.db .yrh

(The Ugarites were a very poor people, and so couldn't afford vowels.):

#2 Scholars have defined the issue pretty tightly, so, for example Tammuz isn't a dying and rising god because he's really a demi-god, not a fully vested, tenured god. So, see, there really were no dying and rising gods. QED.

Or, yeah, Osiris did die and get resurrected and go to Egyptian heaven, where he judges people and gives his followers eternal life—but his resurrection was to heaven, not to Earth, see, so it wasn't really a resurrection. So there really were no dying and rising gods. QED.

Because the scholarship is so narrowly defined, it doesn't touch on questions people like you or me would like answered. Questions like, "Well, is it possible there's a relationship between Osiris—a pre-Christian godman who died and got resurrected and now lives in heaven and judges the dead, and Jesus—a godman who died and got resurrected and now lives in heaven and judges the dead?"

Still, none of that is Dr. Metting's fault, and he's written a fine, readable book summarizing the state of the (narrow) scholarship.

Available only at Amazon .com.

The Homeric Epic and the Gospel of Mark
by Dennis MacDonald

Turns out the ancients had this literary convention called "mimeses," in which they deliberately mimicked the structure and ideas of other ancient writers, in particular Homer. That, says professor MacDonald, is what the New Testament writer author Mark did with his gospel. Which means, some "facts" about Jesus were borrowed direcly from Homer's Iliad. Who'd a thunk it?

Sound nutty? Yes it does. Which is why the professor supports his thesis with oodles of ancient evidence, and a meticulous, rigorous reasoning. There's so much evidence, it's can be tough to keep going. You may well groan, "Enough already, you've convinced me!"

	A non-apologist New Testament scholar's analysis of the Christ-myth
	Basically another Jesus theories book.

Is this the final word on who Jesus was or wasn't? No, it's not. It is a useful look at the methods and conclusions of modern New Testament scholarship—by an academic who isn't impressed by either.

Price is an academic who understands the orthodox scholarly theories, though he doesn't buy them. His theme is that nothing we know about Jesus is historical, everything is mythical.

The book follows the regulation scholarship, starting with the "Jesus People," (an academic term for Jesus' first followers; the Jesus People weren't really Christians, since they didn't believe Jesus was God or that he had risen from the dead), on to the first groups who worshiped Jesus as God, the Christ-cults (another academic term), through Jewish Messianic expectations, non-orthodox early Christianities and even ancient novels, which reveal a cultural theme of escape from crucifixion.

The point is not one-for-one parallels between Jesus and, say, Mithras or Osiris.  The point is that  the first Christians took the basic ideas of their culture and adapted them to their new faith.

The Jesus Puzzle
Did Christiantiy Begin With a Mythical Christ

by Earl Doherty

	Amateur scholar Doherty lays out his detailed version of the theory that there never was a person Jesus, and Christianity began entirely from a myth.
	a good look at the state of the evidence about a "historical" Jesus

Doherty, like professor G.A. Wells, notices that Paul and the other first century New Testament authors never give details about the Jesus of later Galillean legend. From which Doherty concludes there never was a Galillean Jesus; Christianity started wiht a mythic godman, later generations invented the earthly "history."

Good use of primary sources, but this theory can only be correct if a number of odd coincidences explain away evidence that does seem most naturally to point to a real person Jesus.