has j.k.rowling written any other book?

She has written 3 books which is also related to Harry Potter in addition to the 7 book series. They are Quidditch through the ages, Fantastic Beasts and where to find them and The Tales of Beedle the Bard. Quidditch thorugh the ages talk about Quidditch history and interesting things about Quidditch, while Fantastic Beasts talk about Magical Creatures in the magic world. Beedle the Bard is a book with several tales that suitable for children to read. I have written a review here http://www.bukisa.com/articles/21467_tales-for-muggles-the-tales-of-beedle-the-bard

I think the only other book she has written so far is The Tales of Beedle the Bard. It's really a spin-off from the last of the Harry Potter books because it's mentioned there as being given to Hermione by Dumbledore and, in fact, is central to the plot.