Oliver Sacks' The Man Who Mistook His Wife for a Hat and Other Clinical Tales is a collection of case histories of people suffering the bizarre perceptual and intellectual effects of neurological disorders: varieties of amnesia, losing all sense of connection with a limb or even the entire body, losing the ability to recognize people or common objects.... This edition includes postscripts mentioning information and case histories that came his way after the original publication.
My reaction to the stories in this book might not jibe with a normal reader's. The average reader might think, "This is terrible and scary but rare and unusual and thus not something for me to worry about; thus it's just interesting." By contrast, I had a brain problem that was slowly killing me that required major surgery, and I'm still suffering the effects of the disorder and surgery, so my reaction is "Auuuuggggghhhh!" But it's still interesting to me!
The human brain is amazing, and hearing the ways things can go wrong gives the reader a greater appreciation for all the complicated things that go right without us noticing. It's also surprising how much of it involves music. The methods he uses to diagnose the source of the problems and extent of the effect sometimes surprise as well.
While Sacks seems to be a great healer--better and more involved with his patients than any doctors I've ever dealt with--his writing isn't always as good: he's definitely a doctor first and foremost. His writing refers to a lot of other works, authors, and doctors that his audience might not be aware of, so some things go right over the average reader's head. It's a collection of essays and has the same problem that many collections of essays and short fiction have in that some pieces are much more interesting than others. Since he wrote The Man Who Mistook His Wife for a Hat... in the 1980s, sometimes he'll use a term for the people involved that shocked me given that these days it's recognized as being really offensive and dismissive, even if he doesn't mean them that way and isn't an able-ist. His personal religious beliefs sometimes come into play, sometimes in ways that annoyed me but sometimes in a manner I personally found useful, as when he wondered whether two patients with very serious amnesia still have souls... and in one of them thinking that his soul might have moved on already since the amnesia was so serious that the man remade his personal reality from moment to moment and didn't seem to have an emotional connection to any of it anymore.
This book can be fascinating and I recommend it, though with the caveats that it's somewhat outdated and not always well-written.