Here are some good sources:

Books Medical Botany (https://www.amazon.com/Medical-Botany-Plants-Affecting-Health/dp/0471628824/ref=sr_1_1?ie=UTF8&qid=1494004860&sr=8-1&keywords=Medical+Botany)

Dewick’s Medicinal Natural Products (https://www.amazon.com/Medicinal-Natural-Products-Biosynthetic-Approach/dp/0470741678/ref=sr_1_1?s=books&ie=UTF8&qid=1494004479&sr=1-1&keywords=medicinal+natural+products)

Biology of Plants (https://www.amazon.com/Raven-Biology-Plants-Ray-Evert/dp/1429219610/ref=sr_1_3?ie=UTF8&qid=1494004531&sr=8-3&keywords=biology+of+plants)

Fundamentals of Pharmacognosy and Phyotherapy (https://www.amazon.com/Fundamentals-Pharmacognosy-Phytotherapy-Michael-Heinrich/dp/070203388X/ref=sr_1_1?ie=UTF8&qid=1494004776&sr=8-1&keywords=fundamentals+of+pharmacognosy+and+phytotherapy)

Eating on the Wild Side (https://www.amazon.com/Eating-Wild-Side-Pharmacologic-Implications/dp/0816520674/ref=sr_1_1?s=books&ie=UTF8&qid=1494006419&sr=1-1&keywords=eating+on+the+wild+side+nina+etkin)

The Origins of Human Diet and Medicine (https://www.amazon.com/Origins-Human-Diet-Medicine-Chemical/dp/0816516871/ref=pd_sbs_14_1?_encoding=UTF8&pd_rd_i=0816516871&pd_rd_r=ATDC8YB48N1H2TS7X84C&pd_rd_w=zYebJ&pd_rd_wg=zAAqF&psc=1&refRID=ATDC8YB48N1H2TS7X84C)

Florida Ethnobotany (https://www.amazon.com/Florida-Ethnobotany-Daniel-F-Austin/dp/0849323320/ref=sr_1_1?ie=UTF8&qid=1494006266&sr=8-1&keywords=florida+ethnobotany)

Native American Ethnobotany (https://www.amazon.com/Native-American-Ethnobotany-Daniel-Moerman/dp/0881924539/ref=sr_1_1?ie=UTF8&qid=1494006230&sr=8-1&keywords=native+american+ethnobotany)

African Ethnobotany in the Americas (https://www.amazon.com/African-Ethnobotany-Americas-Robert-Voeks/dp/1461408350/ref=sr_1_1?ie=UTF8&qid=1494006185&sr=8-1&keywords=african+ethnobotany)

Traveling Cultures and Plants: The Ethnobiology and Ethnopharmacy of Human Migrations (https://www.amazon.com/Traveling-Cultures-Plants-Ethnopharmacy-Environmental-ebook/dp/B00EDY6AVM/ref=sr_1_1?ie=UTF8&qid=1494006139&sr=8-1&keywords=traveling+cultures+and+plants)

Plants, People and Culture: The Science of Ethnobotany (https://www.amazon.com/Plants-Culture-Paperback-Michael-2005-12-23/dp/B01NH01YZP/ref=sr_1_1?ie=UTF8&qid=1494005994&sr=8-1&keywords=balick+and+cox)

Websites Quave Research Group (http://etnobotanica.us/) Emory Herbarium (https://scholarblogs.emory.edu/emoryherbarium/) National Center for Complementary and Integrated Health ( https://nccih.nih.gov/) National Center for Natural Products Research (https://pharmacy.olemiss.edu/ncnpr/) Center for Natural Product Technologies at UIC (http://cenapt.pharm.uic.edu/) Journal of Natural Products (http://pubs.acs.org/journal/jnprdf) American Society of Pharmacognosy (http://www.pharmacognosy.us/) Society for Economic Botany (http://www.econbot.org/) Economic Botany (http://www.springer.com/life+sciences/plant+sciences/journal/12231) US National Librar(y of Medicine’s PubMed (https://www.ncbi.nlm.nih.gov/pubmed) Tropicos (http://www.tropicos.org/) International Plant Names Index (http://www.ipni.org) WHO Guidelines on Good Agricultural and Collection Practices for Medicinal Plants (http://apps.who.int/medicinedocs/en/d/Js4928e/) Convention on Biological Diversity (https://www.cbd.int/) Antibiotic Resistance Threats in the USA (https://www.cdc.gov/drugresistance/threat-report-2013/)

Opinion of herbal healing books: Herbal healing books run the full gamut from remedies based on anecdotal evidence to remedies that have been subjected to some level of scientific testing. As with anything else, you would be well advised to check the credibility of the sources used.