I've read a LOT of books on the craft of writing, but only a tiny fraction of all the great books out there on how to write. Here is a review of one for fantasy writers:
Adventures in Fantasy is a textbook for teachers of creative writing. The cover suggests it is aimed at grades 5-9, but I found this could easily be adapted for use in the classroom for any year and is especially helpful for adult writers wanting to explore the craft of fantasy writing.
I'm currently editing The Costume Maker, a fantasy novel about an old gypsy who banishes a rude young customer into a dangerous world of dragons, evil fairies and superstitious gypsies. Only the gypsy's granddaughter can save the girl who has been so mean to her. I had never tried to write fantasy before and was surprised at how much I enjoyed it (my usual genre is mystery). This book is so clear and has some great tasks to try to strengthen your world and characters.
My mistake with this book was to purchase the Kindle version, there are a lot of handy worksheets that need to be photocopied and they didn't come up big enough on the Kindle. The book is so good though, that I've now ordered the paperback as well. If you write fantasy, or you want to try fantasy, this is the book to get.