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.
Ten Speed Press 1991
Steve Trudell & Joe Ammirati
Timber Press Field Guide 2009
Mushrooms of the Redwood Coast Noah Siegel & Christian Schwarz Ten Speed Press 2016
Ten Speed Press
Mike Bueg book found only at Fungi.com