Two good encyclopedias of health conditions are "The Ultimate Medical Encyclopedia: Understanding, Preventing, and Treating Medical Conditions" published by Firefly Books and "The American Medical Association Family Medical Guide, 4th Edition." Both encyclopedias are available for purchase on Amazon.com as of June 2015.
Online encyclopedic sources include MedlinePlus by the U.S. National Library of Medicine and Healthy A-Z Guides by WebMD. Due to the evolving understanding of human medical conditions, printed medical encyclopedias age quickly. Online medical encyclopedias eliminate the problem by updating frequently as new information and research become available. They contain information on anatomy, physiology, diseases, conditions and surgeries.
"The Complete Book of Chinese Medicine: A holistic Approach to Physical, Emotional and Mental Health" is a holistic alternative to Western medical encyclopedias. The "Encyclopedia of Natural Medicine, Revised Second Edition" is another a holistic source of medical condition and treatment information. The American Medical Association and WebMD do not recognize the efficacy of these holistic treatments since there is not enough research supporting the holistic claims.
Since Ancient Egypt, medical professionals of all sorts have been writing and using encyclopedias to compile their contemporary medical knowledge into an easily accessible source. Their students learn from the encyclopedias and add their own knowledge to later editions as their understanding of medicine evolves.