When I began, two that were recommended to me were
All the Rain Promises and More and
Start Mushrooming (a true beginner's book that focuses on "the big 6" edible mushrooms).
I've always enjoyed the National Audubon Society's field guides. Here's their
mushrooming book.
That said, I'm sure I won't come off as preachy if I strongly recommend using a trained mycologist to accompany any gathering trip, at least to start, especially for anything other than really common shrooms - and even then, one can get tricked...our areas are loaded with lots of great, edible shrooms - but also some posers, e.g., from all but up close we've always got what look like nice chanterelles - except the gills aren't quite right (but can come off as close, if you're not used to it), they grew in clusters, and in more open patches (not in shaded woodlots). Omphala (Jack O'Lanterns), not chanterelles, and they're toxic. Word to the wise, and all that.