I think that anyone truely interested in foraging for wild edibles will have at least heard of Euell Gibson, one of the USA's most famous and beloved wildsmen that ever lived. His most noted books are:
- Stalking the Wild Asparagus (1962)
- Stalking the Blue-Eyed Scallop (1964)
- Stalking the Healthful Herbs (1966)
- Stalking the Good Life (1966)
- Beachcomber's Handbook (1967)
You can read a very touching bio here (or google his name):
http://www.wildfoodadventures.com/euellgibbons.html