HarperCollins has a stack of books on sale. After finding the first few, the rest I found by searching authors that I knew published with HarperCollins, so there very well could be a lot more.
Bart Ehrman
In addition to
Forged for $1.99, which I linked above,
Misquoting Jesus is $3.99.
B&N AmazonThe Power of Parable: How Fiction by Jesus Became Fiction about Jesus is $1.99
B&N Amazon
Jesus is $1.99
B&N Amazon
The Greatest Prayer: Rediscovering the Revolutionary Message of the Lord's Prayer is $3.99
B&N Amazon
The Birth of Christianity is $3.99
B&N Amazon
The Historical Jesus: The Life of a Mediterranean Jewish Peasant is $3.99
B&N Amazon
Who Killed Jesus? is $4.99
B&N Amazon
In Search of Paul (with Jonathan L. Reed) is $3.99
B&N Amazon
Excavating Jesus (with Jonathan L. Reed) is $3.99
B&N Amazon
Marcus J. Borg
Reading the Bible Again for the First Time: Taking the Bible Seriously but Not Literally is $1.99
B&N Amazon
The Last Week: A Day-by-Day Account of Jesus's Final Week in Jerusalem (with John Dominic Crossan) is $1.99
B&N Amazon
Unprotected Texts: The Bible's Surprising Contradictions About Sex and Desire by Jennifer Wright Knust is $1.99
B&N Amazon
Biblical Literacy by Timothy Beal is $1.99
B&N Amazon