Describes the case histories of some of Sacks's patients. The title comes from the case study of a man with visual agnosia.^[1]  The book "became the basis of an opera of the same name by Michael Nyman, which premiered in 1986.

"The book comprises twenty-four essays split into four sections, each dealing with a particular aspect of brain function such as deficits and excesses in the first two sections (with particular emphasis on the right hemisphere of the brain) while the third and fourth describe phenomenological manifestations with reference to spontaneous reminiscences, altered perceptions, and extraordinary qualities of mind found in mentally handicapped people."^{[2]" (Wikipedia)}