Here is a provocative conspiracy theory: Jesus was an invention of Roman writers seeking to subvert Jewish resistance. He never existed. Or as Bible theorist Joseph Atwill suggests, Jesus "may be the only fictional character in literature whose entire life story can be traced to other sources. Once those sources are all laid bare, there's simply nothing left." You can read a press release explaining the theory here.
The problem with Atwill's theory (other than the fact that it ruins another provocative conspiracy theory, Holy Blood, Holy Grail) is that there are more convincing, less sensational explanations for the resemblances between the books of Matthew, Mark, Luke and John and the writings of the Roman historian Josephus. Or so argues Robert M. Price, in his review.
Price points out that many other authors have offered theories similar to Atwell's, writing that "...somewhat similar theories of a Roman origin of Christianity and of
Jesus have been proposed by Abelard Reuchlin (whose notorious 1979 booklet The True Authorship of the New Testament
strikingly anticipates Atwill’s at several points),
Margaret Morrison (Jesus Augustus),
Cliff Carrington (who also ascribes the gospels to the Flavians), and Stephan
Hermann Huller (Marcus Agrippa,
etc.). We might find that one of these alternative theories of Roman origins
explains many of the same things Atwill’s does, and without the disadvantages."