There are so many choices for mushroom identification books that it's hard to know where to start. The first tip is to get one as local as possible. Usually these are smaller books with fewer species, but beginners get overwhelmed quickly with too much information. By picking several of the most common mushrooms you see and finding them in a book, you are off to a good start in learning to identify. Listed here are 4 books that focus on mushrooms west of the Rockies in order of usefulness to beginners. If you wear out all 4 of these books, you will know more than you need to know! Be sure to read the introductions; they are full of tips and clear characteristic explanations.
1. All That the Rain Promises and More David Arora Ten Speed Press 1991
2. Mushrooms of the Pacific Northwest Steve Trudell and Joe Ammirati Timber Press Field
3. Mushrooms of the Redwood Coast Noah Siegel and Christian Schwarz Ten Speed Press
4. Mushrooms Demystified David Arora Ten Speed Press