I'm about halfway through Black May right now. It's enjoyable, but not anywhere near as much as Operation Drumbeat. That book really took the reader inside the world of codebreaking, naval intelligence, submarine warfare, planning, sort of like a WWII techno-thriller. Black May is more of a detailed naval history.
If anything, it's hammering home the idea, that I'm starting to hold myself, that the U-boats were incredibly over-rated as weapons of war, and the Germans lost the Battle of the Atlantic by being perpetually two steps behind the technical and tactical curve after mid-1941. The account of the battle of OSN-5 includes so many accounts of U-boats being surprised in the fog at spitball range by radar and HF/DF-equipped escorts, and either getting run over, hedge-hogged, or depth charged, I seriously came close to slapping my forehead.
C'mon guys, the Allies have been fighting you for four years, have broken into your codes, are vigorously training their escort commanders, building more ships than you can sink, and equipping their destroyers and frigates with the latest sub-hunting and killing toys. Why are you swamping the ocean with obsolete submarines manned by inexperienced crews on their first patrol?
Yeesh. I'm starting to think that Karl Donitz should have a statue alongside Nelson in Trafalgar Square. He saved the British a lot of trouble sending so many of his men to stupid deaths.