However, J.K. Rowling still made pains to give us as many details as she could in the original Harry Potter books. Plus, she dropped a few clues after they were published, as she is notoriously wont to do . Before you head to the cinema to see Fantastic Beasts: The Crimes Of Grindelwald this weekend, here's everything we know about Dumbledore and Grindelwald so far, according to the books.