"Hunt and Kill: U-505 and the U-boat War in the Atlantic,:" edited by Theodore P. Savas and written by most of the giants in the field (that would necessarily exclude me), and "Steel Boat, Iron Hearts: A U-boat Crewman's Life aboard U-505," by Hans Goebeler and John Vanzo. Both can be seen here:
www.savasbeatie.com.
Cheers,
tps