Here are five books that will give you a solid understanding of the new testament and the latest scholarship on it:
Jesus: Apocalyptic Prophet of the New Millenium by Bart Ehrman. Expounds on the widely accepted view that Jesus was a failed doomsday prophet, as well as delivering a solid beginner’s level understanding of Christian history.
Scripting Jesus by L. Michael White. White faithfully delivers a good report on the latest in New Testament scholarship, in addition to all of the basics. No apologetic agenda here, just a fair look at history. I frequently say that if you only read two books on the New Testament, read Ehrman’s and White’s, because that is how well I think of them.
The Mystery of Acts by Richard Pervo. Pervo smashes some common fallacies in historical reasoning, and manages to demonstrated that the book of Acts is really just church propaganda from the second century, not a reliable history.
Evolution of the Word by Marcus Borg. It’s a new testament written in chronological order with a timeline of the years in which the books were written. Good reference work.
The Incredible Shrinking Son of Man by Robert M. Price. Although Price occasionally goes too far with his speculations, this is a good book for several reasons: because he shows an awareness with methodological problems that you often don’t hear from New Testament scholars (i.e. The criterion of dissimilarity is probably invalid, Hypothetical sources like ‘M’ and ‘L’ may not have existed [which is a widely shared but rarely admitted conclusion]). You’ll also hear some theories which scholars rarely entertain but which, as far as I can tell, are correct (or at least plausible).