What I would love to know more about is the history of, and predecessors to, the Great Forage Revival that we are now witnessing. Now you can read and learn from Rebecca in the United Snakes of AmeriKKKa, from Patrick in the People's Republic of Abba and countless of others but before that where did you learn the stuff you need to know to be a successful un-poisoned forager? My working hypothesis is that every country had its own tradition and its own specific history with distinct differences in motivation and focus. In 2006 Richard Mabey wrote an article for the Guardian about his foraging antecedents and the broad picture he creates is of modern foraging as a hippie discovery of WWII Governmental publications promoting hedgerow harvests to make ends meet. The American forage tradition, by contrast, seems to be guided more by long Native American traditions. But this is guesswork.
The book that Mabey misses in his piece but which is undoubtedly the foraging guide with the highest print run in the entire world is John Wiseman's 'The SAS Survival Handbook'. It's easy to understand why the foragers I think about would fail to acknowledge a military curiosity like that: it's typical for instance that the SAS Handbook dwells extensively on poisonous plants and trees while Mabey's 'Food For Free' barely mentions them. To a soldier foraging is a struggle for survival in a dangerous and cruel world while the hippie forager sees foraging as a rediscovery of nature's gifts. The pics here are screenshots from a copied edition of the SAS guide downloaded from the Pirate Bay. Another Army survival guide with plenty of foraging material can be found here.