One of the finest books about Submarines in WW2 is "War Beneath the Sea", by Peter Padfield - covers the submarine operations of all nations and puts them into perspective. There is a semi-official history, with the accent on the RN, by Cdr Richard Compton-Hall - The Underwater War 39-45. Technical details of the world's WW2 submarines is in Ermilio Bagnasco's aptly-named "Submarines of World War Two". Try Googling for the above or look at Amazon.
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