Extreme Programming Explained: Embrace Change, Second Edition by KentBeck, CynthiaAndres
ISBN: 0321278658 New edition of the classic.
A summary and quick overview of the differences between the second and first edition can be found here: http://xp123.com/xplor/xp0502/index.shtml
Arguably a second volume rather than a second edition.
The second edition is a far more powerful, complete, and inclusive book than the first. The new testament. -- PeterMerel