Depends on what you count as a philosophy book. As if you count Starship Troopers as one. Since it's basically Robert A. Heinlein's views and philosophy on culture and how the government should fuction and explaining why it should be. Sadly the movie was made by someone who hated it and try to change the story to make them "fascist" though the first movie, he was only the director and couldn't change the script. Though if you don't count that. I would say "Book of Five Rings"