I've never read the book, but I spend a lotof ttime reading KTBs on uboatarchive.net. They're incredibly interesting and helpful in playing realistically. It also gives you some insight into why some Commanders were hugely successful and some weren't. Hardegen's actions during his 2 East Coast patrols are incredibly gutsy. He'd usually close to 500m surfaced; as a result he only missed twice on his Drumbeat patrol!
http://uboatarchive.net/KTB123-7.htm
BTW that shot at Malay happened at dawn, Malay had spotlights on U-123, another steamerffiring starshells, and there was only 10m depth under keel. He had to fire and get the hell out of Dodge.
T