Probably, having watched the movies several times to the point you can quote them. Being able to quote parts of the books, owning different versions of the books and movies. Owning T-shirts, costumes, jewelry, replicas, pictures, and other random things that are somehow related to the movies/books. Listening to music from or inspired by the movies/books. Considering naming a pet or child after a character from the books/movies. Um mm, I can't think of anything else. But I gave you an example of an extreme fan, is that helpful? Hope it is, let me know!