^ I think i read (ahem lol, the friend of a cousin of the wife's father-in-law...) somewhere that Werner sank two ships, however it is possible he had served on other boats which' captains
did sink other/more ships, or he did it in the position as a 1. WO or something on those boats.
As said before i believe he was real, however his book is not to be taken literally, when it comes to events he himself experienced as a commander. It is a (good) mix of real events, but he probably did not live through all of them himself. It is a novel, but (i still think) quite a good one. A lot of his observations and technical details are true.
edit Aktung how are you still awake