Disclosure: I love Oliver Sacks and miss his voice on NPR science programs greatly. He always spoke thoughtfully and provocatively. This book was first published in 1987. Neurology has progressed exponentially in the past 30 years, so treatments and understanding of these kinds of cases have progressed, as well. The language he uses in his case studies is a bit anachronistic (people are labeled with names that were medically correct at the time, but make modern folks flinch.) At that time, these people were often institutionalized (where Sacks encountered them). Now most would be treated at home or in smaller group home situations. 
 In spite of its limitations, I enjoyed the book. Sacks expresses a profound compassion for his clients. The purpose of the book was to show the humanity and dignity people with terrible neurological disabilities can have: Downs Syndrome twins who communicate in prime numbers, autistic children who express themselves with incredibly detailed art, a 57-year-old navy veteran with no short-term memories after age 20 who finds peace and meaning in gardening. If you looking for cutting edge neurology, read another book, but this one is a model for how to look at and treat (as in attitude, not medically) people with disabilities. An interesting pairing with a new book on autism: NeuroTribes: The Legacy of Autism and The Future of Neurodiversity--one of my favorite reads this year.