Peterson Field Guides: "Mushrooms" by Kent McKnight and Vera McKnight
Smithsonian Handbooks: "Mushrooms" by Thomas Laessoe and Gary Lincoff
"Simon and Schuster's Guide to Mushrooms" by Giovanni Pacioni
"National Audubon Society Field Guide to Mushrooms" by Gary H. Lincoff
"Mushrooms of Northeast North America" by George Barron
"Lichens of North America" by Irwin M. Brodo et al