The most recent popular book by Bart Ehrman, James A. Gray Distinguished Professor in Religious Studies, is Jesus Before the Gospels: How the Earliest Christians Remembered, Changed, and Invented Their Stories of the Savior (HarperOne, 2016). In the book, Prof. Ehrman examines the role of memory in the earliest transmission of stories about the historical Jesus.
For an extensive two-part debate (hosted by the “Unbelievable?” radio program) with Richard Bauckham on the relationship of the New Testament Gospels to eyewitness testimony, see the following links: [part 1] [part 2]
The following is a 28-minute interview (with the American Freethought podcast) in which Prof. Ehrman discusses some of the main points of the book (the actual interview begins at the 2:44 mark; see also YouTube):