I find Michael Pollan to be a really engaging writer, with the prose easy and enjoyable to read. The fact that I learn so much while reading one of his books is just a bonus. The only real issue, which also relates to books like Ayelet Waldman's A Really Good Day, is that I want to try these drugs to see what effect they have on me; but I'm far too risk averse to try wandering down to the bad area of town to try and score some.

I found the section of Opium to be particularly interesting, as I have Oriental poppies growing in my own garden. The section on mescaline was also very interesting, especially the cultural issues around it's growing areas and usage.

If you enjoyed How to Change Your Mind, this is more of the same, and worth your time.