The best portrayal of Hitler and Himmler I have found was in a book entitled "Unto the Beast" by Richard Monaco. Unfortunately, the book itself is not all that great. A fine description of Hitler's youth in Vienna and service in World War One is muddled in with an absurd sword/sorcery-type plot about raising the Devil and his demons to save the Reich. This book will give you a reason for the Holocost that only Aleiser Crowley could believe.
The oddest portrayal I have found was in a novel written in the Seventies entitled, "Hitler Has Won". Through several twists and turns in the plot Hitler wins WW 2, but ends up being elected Pope!!
My jaw fairly dropped at that one. Talk about Chutzpuh in an author! 
Can you add any more to this list? Any fictional book, be it war story, super-spy tale, or political thriller will do.
