After a bit of searching on Amazon.com, I found out that there were no XNA books targetting XNA GS 2.0. But there were three books due in late february that could be of interest for us.
I'll list them in no particular order:
1. Essential XNA 2.0 Game Programming (Paperback)
by Jim Perry (Author), Allen Sherrod (Author) (Paperback - Feb 25, 2008)
2. Microsoft® XNA Game Studio 2.0: Learn Programming Now! (Paperback)
by Rob S. Miles (Author) (Paperback - Feb 23, 2008)
3. Professional XNA Programming: Building Games for Xbox 360 and Windows with XNA Game Studio 2.0 by Benjamin Nitschke (Paperback - Feb 26, 2008)