There have been quite a few books in the past few years making the case that there was no historical "Jesus of Nazareth" - that there was no actual person that led disciples, healed the sick, was crucified by the Romans, and whose teachings formed the basis of the Christian Religion.
This is not a new notion - Gerald Massey wrote of it extensively in the 1880s. Massey proposed that the early church fathers took a figure who was originally mythical and retrojected him into history as if he were a real person. This is why the earliest Christian writings - the letters of Paul - which came BEFORE the Gospels were written - do not ever mention any of the things about Jesus' (alleged) life. Paul's letters do not even mention anything "the historical Jesus" is alleged to have done or said; they do not even suggest the idea that Jesus was a man who had recently lived.
The DVD "The God Who Wasn't There"
http://thegodmovie.com does a nice job of getting this idea across in a powerful and compelling way.
The writings of Earl Doherty - to be found online at
http://jesuspuzzle.com - are IMHO the most compelling and most thoroughly documented case against the notion of a historical figure Jesus. Doherty makes an air-tight, interlocking, inescapable argument that early Christians worshiped a heavenly Christ figure, not a man who had recently lived. Doherty's site is highly recommended, as is his book, "The Jesus Puzzle".
Tom Harpur's "The Pagan Christ" gives an excellent overview of the massive erudite works of Gerald Massey and Alvin Boyd Kuhn. It is especially enjoyable to read as it is also a narration of Harpurs's own de-conversion from Literalist Christianity.
I'm just finishing Freke and Gandy's "The Jesus Mysteries", and I can emphatically say that this is THE best book on the origins of Christianity and the creation of the fictional-turned-historical character Jesus. It is very comprehensive and extensively documented. The argument is very coherent, and while Doherty does an excellent job of proving the early Christians did not believe in a historical Jesus, Freke and Gandy do this AND they also demonstrate HOW the Jesus Myth was derived from Pagan sources, and how it was a natural, predictable outcome of the Hellenistic influence on Judaism. They show how the Egyptian/Greek dying/rising godman/savior concept was adapted to Judaism by grafting the classic Dionysus-Osiris myth elements onto the Jewish Messiah concept, thereby producing the Jesus Myth.
Freke and Gandy further show that early Christians (i.e. Gnostics) did NOT take the myth to be history, and that Christianity as we know it today emerged when one later type of debased Christianity - Literalist Christianity - mistook the myths for history and then systematically suppressed all rival interpretations and systematically destroyed all evidence that documented their plagiarism and forgery.
Earl Doherty's website articles are even better than his book "The Jesus Puzzle" - and they are free. Although I loved that book, and Tom Harpur's "The Pagan Christ" too, I think that Freke and Gandy's "The Jesus Mysteries" is overall the single best book on this important (and largely ignored) topic.