As I’ve written elsewhere, Osprey military books can vary in quality. This one scored big, discussing. The development, engineering and tactical employment of the various American sub classes of WWII and how they helped to cripple Japan’s maritime logistics. The subs excelled at rescuing downed fliers and took out a fair share of warships as well.
I caught one mistake when the authors misspelled the name of the Imperial Japanese Navy’s Hayanami as “Hiyami”, but that might have been an error in their sources. There were probably other mistakes as well, but I don’t anything deserves to cost this book a star.