I think Das Boot was well done for its time, but I have tosay that The Enemy Below is one of my favorite WWII movies. I have not read theBook on either, but you cannot expect the book to be the same as the movie, butI’d agree that movies do change the book to much. http://www.youtube.com/watch?v=YOGu9EP7ZUI
For its time? Das Boot was made in 1981. And it was also an adaption of a (somewhat autobiographic) book writen by Lothar-Günther Buchheim, a Kriegsamarine veteran.
I don't think you can really compare 1950's acting with a movie made to show real terror of being in a steel tube hammered by depth charges one day and mind numbing dullness of patrol duty the other day.
Was this Herbie's only movie role? I think so.
While Buchheim's portrait of his own role is a bit dubious (turning himself from a Nazi propagandist into a doubting submarine Private Joker), his book and movie is unique insofar as he caught the way people talked back then perfectly.
The dialogues are the heart of both, and the language.