For a remarkable and insightful book on cannabis sativa, I would suggest reading Marijuana Reconsidered by Lester Grinspoon. The book provided the first real scientific investigation into the psychedelic properties of cannabis sativa. I found the section by Mr. X (Carl Sagan) to be informative, accurate, and humorous. The fact that marijuana was documented, by William Osler, long before the 1930’s to be the most effective cure for a migraine was a complete surprise to me. I highly recommend this book and any other by Lester Grinspoon.