There is a scene from the 1960s movie version of Fahrenheit 451 where the captain is explaining to Montag what books are about. He ends with the line, "We must burn the books--ALL the books," and when he says those last three words, the camera points to Mein Kampf.
If you want to understand evil and why it succeeds before it fails, Hitler would be a good a case study as any, and better than most. Someday there will come a Superhitler, the Antichrist, and understanding Hitler will help us to recognize him, for the one thing he won't look like is what we assume evil looks like.
A great film...one of my favorites.