I was underwhelmed with the first third or so of the book, it felt a lot more academic and like the author was trying to persuade his side vs just presenting facts. By the end I really enjoyed it and it felt a lot more accessible to a non-researcher. McKenna puts forth several interesting ideas about drug usage, plant medicine, feminism, and the evolution of humanity and language. The book had great coverage on psychedelics and their historical usage in both animals and humans, especially with traditional shamans.