Looking for a good non-fiction book related to 20th century world history

Hi everyone! I'm doing a college assignment and need to pick out a college level, nonfiction book relating to any person, idea, subject, or event pertinent to 20th century world history. I'm really not picky when it comes to books, so if you have a favorite, drop it in the comments and I'll check it out! (Also wouldn't mind adding some books to my personal list). Thank you!