There's a few good ones I bought but I can't remember them all...
Here's a few good ones:
U-Boat War Patrol: The Hidden Photo Diary of U-564 (
http://www.amazon.com/gp/product/1591148901) written by a Subsim member!
Iron Coffins (
http://www.amazon.com/gp/product/030681160X) was spectacular as well.