"Misquoting Jesus: The Story Behind Who Changed the Bible and Why" by Bart D. Ehrman.

This is a kind of a beginner's book for people who are interested in the ways that New Testament manuscripts were altered and modified, intentionally and unintentionally, by copyists and translators before the invention of the printing press (and the interpretations of those different versions up to the present day). It's written in a much simpler style than many other scholarly works on the subject of early-Christian research and exegesis (including other books by the same author).

As with most works of this type, Ehrman has a bias in his interpretation of the available data, but Ehrman makes his opinions quite clear and explains in his introduction the unexpected path his own belief has taken that has led him to form those opinions. He was "saved" during the evangelical push of the early '70s and attended the ultra-evangelical Moody and Wheaton colleges, but his research and even his education caused him to question and finally to reject the fundamentalist agenda.

If you too have come to the realization that not every word in the Bible is literally true, if you wonder whether the Gnostics were really so heretical after all, if you're not ready to slog through a tiny-fonted tome by Elaine Pagels or Bruce Metzger, then try this book!