This book made me respect Hoffman even more, because he includes a key bit of material on DMT use by South American Indians. I am a strong proponent of psychedelics (or entheogens) being usable therapeutically. But like any pharmaceutical, there can be problems, and not everyone responds biochemically in the same way. We are all mutants.So this note about the one tribe that became hyper-violent is something I am glad he included. Hoffman was a good scientist, and like any such, he didn't shy from problems.Overall, this is a classic, well worth having on the shelf.