I actually had the pleasure of being given an autographed copy from from Mr. Williams at the 2008 Libertarian National Convention. Had I not been given it, I might never been aware of this work, much less read it. It's a nice weekend read, Mr. Williams goes through the history of specific drugs from who discovered/invented them to what their uses were prior to being banned in the United States; he offers extensive facts and figures that really help one understand the fruitless nature of the war on drugs. Most importantly though, Mr. Williams isn't just another detached author writing on this topic, he has quite a number of colorful personal experiences with each of the drugs he describes. Put it all together and any reader can obtain a general understanding of some major drugs, what they're like, their history, the laws surrounding them today, and why we shouldn't be afraid of them.
My only complaint about this work was that there were no citations for his figures. I do not doubt Mr. Williams but it would have been nice to know what he was referencing (he does make a few references, but not many) so that I could do further research or use his book for academic citations.