Stalking the Wild Asparagus by Euell Gibbons was published in the 60's as a serious and I believe the first popular exploration of wild food. It was also the subject of much hilarity of the SNL variety (ala Eating the Wild Redwood Table) after the Euell appeared on TV ads for Grape Nuts cereal.
Gibbons taught where to find, how to recognize, how to harvest and prepare many wild plants for food. He also wrote about some wild game but that part never interested me so I can't really comment on it. He wrote in a conversational style that made one feel included as he explored the wild plus the more domestic but unlikely-to-be-thought-of-as-food plant sources. Included among these and personally tried by this old hippie noder were cattail flour, daylily buds, sassafras tea, Touch-me-Not seeds, Jerusalem artichoke tubers, dandelion greens and wine, acorn flour, morel mushrooms, wild strawberries, serviceberries and ramps. Ummm ummm good, and fun - back before Fresh Fields and Sutton Place Gourmet.
Wow! unconfirmed but interesting addendum added after this ching..."QuantumBeep says re Stalking the Wild Asparagus: Hmmm. It bears noting that Euell Gibbons died by... eating the wrong plant." Still, even if true, I don't think it was any of the plants in the book that killed him...and I did live through the ones I noded above. I would say don't eat those pretty pokeweed berries!!! Seriously, we have enough resources now that no one need eat any unindentified things...food and informational resources...and it was a good first book in the field.