That was a very rich book. it's is nominally "hallucinations", but it's range is extensive.
The author, Oliver Sacks, is a knowledgeable neurologist and neurosurgeon passed away not too long ago, but his experience was intense. I learned that he experimented with hallucinogenic and other drugs when he was younger, and he used his experiences and knowledge of the brain and human reactions to inform himself and the scientific community of pluses and minuses of all types. I respect the fact that he realized that his one and only experience with opioids was enough for him, and he consciously decided not to do that again!
Explorations of near-death experiences and out of body experiences and how they relate to the brain and reality are great. And the comparison with God and God-like experiences are convincing and satisfying, perhaps more so for non-God believers – like me – then for, say, fundamentalists. Relating all kinds of things with hallucinations as opposed to "spirits" or "extrasensory" experiences is encouraging and paints a picture of reality as opposed to magic. I really liked this book!
I have read part of The Man Who Mistook His Wife for a Hat, and I now feel that I need to go back and reread the entire thing. He's humorous but serious, and he emphasizes the amazing things that the mind can do. Excellent author!