If you want to be a good historian or even an RA librarian you need to utilize multiple resources. Websites like the ones you will find here will provide you with quality resources. These sites provide books in both Non-Fiction and Fiction. They will be quality resources for the history buff and the librarian alike. If you are a librarian these sites will be useful to you in that you will be able to find a multitude of resources for both entertainment and reference.
Bookriot is a readers advisory website that provides articles about books for both entertainment and research. This website has an article that provides the top 100 books that contain World War II information. Link
Goodreads is considered one of the most popular reader websites. This website also provides list that can assist librarians and researchers with quality resources regarding World War II. Link.
Bookbub is another readers advisory website. Bookbub has a list of descriptions of 22 books that are Non-Fiction resources. Link.
John Keegan is a historian who wrote a book called The Second World War. At the end of the book he provided a list of the fifty best books that he used for research. This website provides that list and categorizes them by time periods during the war. Link