Amazon.com: A Primer of Drug Action: Books: Robert M. Julien

Buy this book. I used it in my Psychopharmacology class in college (and I went to a really prestigious college). It gives a neutral, balanced look at the benefits and true risks of drug use. You will see side effects listed but there is nothing fabricated about it. This book initially convinced ME to change my own position on whether cannabis should be legalized - before I ever tried the drug for myself. In fact, this book made me feel comfortable enough scientifically with cannabis to try it without fear.

It's a great textbook. It does require intellect and education to understand drug metabolism, but a lot of the information that you will need about risks and such is in layman's terms.