Most of the WWII books I have read are non-fiction. You ought to see my library...woops, you have!!!
I just found a CD that is entitled "Six Months That Changed The World" It is the Treaty of Versailles and the Road to WWII. It actually is a University course by Margaret MacMillan. I am looking forward to listening to it. Right now I am listening to a CD that deals with all the things they did not teach you in High School about History. It is fascinating how much is left out of our High School History classes. Real shame. They don't teach the kids to think and reason, just memorize facts.
I just remembered a good author on books about WWII...Herman Wouk. He wrote epics "The Winds of War" and "War and Remembrance". Both excellent.
Another good story, that does not have to do with WWII is "The Rising Sun" By Douglas Galbraith. It d takes place in 1698 when 5 vessels led by the flagship "Rising Sun" embark from Scotland to what is now Panama and their adventures and hardships. It is an exciting read. I had never quite read anything like that before. When you read about these pioneering people who were brave enough to leave a semi secure homeland (well, it was familiar) and venture out into the unknown, it really makes your heart go out to them. It is very fascinating. There were 2000 that started out and only 300 came back. A real tragic story.

The classic post-WWII alternate history is, I think, Philip K. Dick's "Man in the High Tower". Long before "Fatherland", PKD envisioned an occupied America with his usual creativity and flair.