I know that in any kind of societal collapse, whether economical, militaristic/terroristic, or Mother Nature reminding us we're not in control(like Yellowstone supervolcano blowing), you can expect to not have access to medical services like we do now(of course sometimes the quality of the medical care is crap anyways, but that's another topic). I've been researching herbal medicine for a while, and my favorite books are Rodale's Illustrated Encyclopedia Of Herbs(it lists history, cultivation, and whats uses the herbs have. Technically it's not a medical herbal book, but it has such a wealth of info I consider it one. Only downside is I don't think it has enough color pictures of the herbs, just b&w illustrations). My other favorite is The Complete Medicinal Herbal by Penelope Ody. It not only says what herbs are good for what, it tells you how to make the medicine from them. It doesn't include ALL medicinal herbs in the main section, but there are charts in the back with a host of medical conditions and what herbs can be used to treat them(including ones not described in the book). The Eyewitness book series, their one on herbs is also useful, but like Rodale's book, not strictly a medicinal herbal book. I recommend always having more than one source of info for home medicine to compare notes between different authors' preferences. I have been trying to learn herbal medicine for pets too, but I haven't found a good holistic book on dog care yet, but The Natural Cat by Anitra Frazier is good. I know there's one more herbal medicine book I really like, but can't remember the title/author and I can't find it. I swear I kept them in my homesteading library, but it's not there. Oh and as a side note, best place to buy seeds/plant of medicinal herbs is Horizon Herbs(Horizon Herbs-Organic growers of medicinal herb seeds, medicinal herb plants, organic vegetable seeds and organic garden seeds.