In addition to the one above, HarperCollins has a number of interesting books for $2.99. This is a publisher sale, so if you don't like the retailers I've linked, you can search your favorite store using the ISBN.
The Historical David: The Real Life of an Invented Hero by Joel Baden
eBooks.com Amazon ISBN: 9780062188335
The Misunderstood Jew by Amy-Jill Levine
eBooks.com Amazon ISBN: 9780061748110
Jesus, Interrupted: Revealing the Hidden Contradictions in the Bible (And Why We Don't Know About Them) by Bart D. Ehrman
eBooks.com Amazon ISBN: 9780061863288
Commentary on the Torah by Richard Elliott Friedman
eBooks.com Amazon ISBN: 9780062240934
Jesus: Uncovering the Life, Teachings, and Relevance of a Religious Revolutionary by Marcus J. Borg
eBooks.com Amazon ISBN: 9780061745553
Scripting Jesus: The Gospels in Rewrite by L. Michael White
eBooks.com Amazon ISBN: 9780061985379