The book "Who Wrote The Bible?" by Richard Friedman is the best single source I've found for explaining the origins of the Torah.
The "Documentary Hypothesis", now almost universally accepted, posits that the "five books of Moses" were in fact written by at least four people as late as the return from exile. Friedman explains and illustrates this explanation in a readable, even entertaining, yet still precise, fashion.
Has anyone here done real research on the Documentary Hypothesis and yet found it unconvincing? If so, why?
Here's a link to the Barnes & Noble description of Friedman's book:
http://shop.barnesandnoble.com/booksearch/isbnInquiry.asp?isbn=0060630353