For your next read, try Edward Beach's Run Silent Run Deep.
I think people are being a bit hard on Iron Coffins.
It is a great read and I am sure there are many of us for whom this was one of the first submarine books we read.
The story that Werner tells is true even if some number of the facts are not. Life on a WWII submarine is mostly boring so Werner, in trying to "tell his story" had to speed things up, combine things, and even fill in literary holes.
If one is looking for an encyclopedic read like Clair Blair, Werner's book is not for you.
If, however, you are looking for a perspective into the human aspects of German WWII submarine life, Werner's book captures the humanity.
I have read a few submarine books in my time and few have been able to describe the human side of the German navy like Werner's book.
Why would anyone be surprised at an old navy guy telling war stories that are not 100% factual?

Perhaps he should started the first chapter with "there I was, no <expletive>, staring death in the face....