This may have already been posted but I didn't see it earlier... While doing an internet search, I found an electronic version of the 1943 Submarine Commander's Handbook (U.Kdt.Hdb) posted on the Historical Navy Ship Association's website, translated into English. I haven't had a chance to read all 65 pages, but it looks fairly good even if some of the tactics had become outdated by that time due to Allied advances in radar. The link is
http://hnsa.org/doc/uboat/index.htm#par150.