Ditto to Cunningham!
I’m still learning but have a few sources I use a lot, including the Cunningham book.
I also like A Master Grimoire of Oils, Herbs, and Incenses by Pat Kirven Sawyer and witchipedia.com
I’m also reading this currently- Herbal Magic Correspondences Guide by Briana Blair and working on integrating it into my plant info spreadsheet here which I hope can also be helpful (it is based on Cunningham’s and Sawyer’s books). I update it whenever I can
Consider two Tarl Warwick books, Fruits of Eden and Folk Medicine: A Collection. The best books on gardening will be about your local area, or you can do some container gardening wherever you are.
Oh and if you want modern day cunning man stuff that you can use every day, as in materia medica, search “Dave Canterbury materia media” on youtube, he has a playlist that shows you how to identify and forage for these medical and edible plants in the US. This is from a self reliance or survivalist perspective.
Finally, our very own BALG has published the “Herbarium Diabolicum” which has a bit of both these, focusing on a few psychoactive plants from an LHP persepctive.