There was a lawsuit over a guide to Harry Potter that Rowling won, but she won it because the guide copied too much from her books. They were later able to publ

There was a lawsuit over a guide to Harry Potter that Rowling won, but she won it because the guide copied too much from her books. They were later able to publish it by cutting down on the quotations. https://en.wikipedia.org/wiki/Warner_Bros._and_JK_Rowling_vs._RDR_Books https://en.wikipedia.org/wiki/Warner_Bros._and_JK_Rowling_vs... The courts acknowledge that reference guides to fictional worlds are either non-infringing or transformative fair use. You can't copyright fictional facts either, only the expression of them.