Good reference guides for fantasy writers are few and far between. I know, because I've pawed through most of the options. I took a shot in the dark in purchasing Alchemy With Words, volume one of The Complete GuideTM to Writing Fantasy. Published by a small press and written by a collection of fantasy authors who haven't much collective experience or acclaim among them, the book has much to recommend it--and much not to.
On the plus side, this is one of the most varied and complete offerings I've seen on the subject (and this is just volume one). Subjects include Roots of Fantasy, Characterization, Race Creation, World Building, Clichés, Plot, Medieval Clothing and Food, Health and Medicine, Magic, Mythology, Religion, and Arms and Armor. Although a few chapters skim by with only basic info, many of them include insightful and detailed explanations of aspects of the genre that every author would be wise to heed. Of course, with only a chapter devoted to each subject, the book can't be considered definitive. But it offers an excellent jumping-off point into further research.
Based on the quality of information alone, I consider the book worth reading. However, the production values offer some serious drawbacks. Aside from general poor editing and typesetting, the lack of professionalism displayed by the various authors--some to the point of out-and-out self-indulgence, in which the authors ramble about their own unpublished fantasy manuscripts or state their subjective pet peeves as if they were rules of the genre--is annoying at best and downright frustrating at worst. If you can get past the writing to access the information, you may find this book a useful primer on the world of writing fantasy.