This book is the most comprehensive history of cannabis prohibition that I have found. If you've ever wondered about the real reasons behind why this harmless herb and its relative, the amazing fiber hemp, are illegal, you should check this book out for sure! The truth will astound you.
Then, because this book was published in the 1970s, you should check out The Emperor Wears No Clothes by Jack Herer for a more recent look at the bogus science, racism, and government trickery that have helped keep this plant more illegal than methamphetamine.