You can judge this book by its title.
Illegal Drugs: A Complete Guide to Their History, Chemistry, Use, and Abuse (2003) by Paul M. Gahlinger MD is, in fact, an extremely comprehensive treatment of both illegal and legal psychoactive substances, including their history, law, chemistry, processing and distribution, metabolism, neuroscience, medical management, linguistics, folklore, and popular culture. Hundreds of drugs are covered, from the more common ones such as marijuana, cocaine, heroin and methamphetamine to drugs which I kind-of-almost-never-heard-of such as ibogaine, cathinone, peyote and bufotenine. The book is truly a tour de force on the subject of substance abuse.
Most of the information in this book has stood the test of time. For example, according to the author, “tobacco is the most injurious drug in the world today.” This was true when Illegal Drugs went to print in 2003, and it is equally true today. I nonetheless believe that readers would benefit from an updated edition of this book because there are now newer, incredibly dangerous drugs on the street. These include drugs that cause terrible soft tissue necrosis and old drugs with new and horrifying side effects. Further, drug laws have changed, sometimes dramatically.
Despite the above-mentioned minor limitations (and the fact that ethanol abuse isn’t mentioned at all), the book makes for a terrifically interesting, informative and enjoyable read. I recommend very highly to both physicians and laypersons who are interested in psychiatry, psychology or toxicology.