This one is free on Kindle, but not sure if it is so world wide or only Europe:
Got it free here to in Australia. Thanks for the link rocketman.
This one is free on Kindle, but not sure if it is so world wide or only Europe:
Silent Victory, Clay Blair Jr.
This is a must read if you have any interest in the US sub war against Japan.
Wahoo, Richard O'Kane.
O'Kane when he was an XO.
Iron Coffins, Herbert Werner
One of the best accounts of day to day Uboat operation I've ever read. You find yourself cheering him on even though he is the "Bad guy".
Steel Boat, Iron Hearts by Hans Goebeler.
Goebeler served aboard U-505 until its capture by the Americans. U-505 is now a museum in Chicago which Goebeler gave tours on his old boat until he died.
War is a Racket, Brigadier General Smedley D. Butler
This is more of an essay and is written pre-WW2 but its a quick read that is highly recommended.