I don't think I've actually read a nonfiction book that wasn't for class in, like...ever. And I do mean ever. Unless Badass of the Week counts? It is about real people! Admittedly I do not read it in book form, but. Real people! And...I have read things that contain characters based on real people? But I'm not sure the Kuroshitsuji arc guest-starring Arthur Conan Doyle counts.