A nice overview of the issues and controversy surrounding the use of cannabis. Understanding Marijuana addresses the evidence and current state of knowledge about issues such as cannabis history, gateway effect, impact on thought and memory, subjective effects, pharmacology, physical health effects, medical marijuana, social issues, law and policy, and treatment of problematic cannabis use. Earleywine cites resources and research to support his conclusions and yet presents the evidence in a very readable and well-organized manner. This book is a great overview for anyone interested in learning about cannabis, but might be a little overly simple for those who are already very knowledgable in the field. Also, due to its comprehensive nature, would serve as a reasonably good reference for finding source materials addressing particular cannabis issues.