The book is an exploration of the complex human mind, an exploration of individuals under a palette of brain malfunctions. Oliver Sacks reveals some of the spectacular cases he encountered as a neurologist and explains each case’s particularities - the physiological implications, the associated syndromes, the social blockages. He approaches each case, not just from a medical perspective, but with a peculiar sensitivity, with the philosopher's eye. He criticizes the classical approach of neurology and medicine that tends to reduce a human being to a pure mechanized system, rather than see it as a personalized soul with unique character. He gets deeper, exploring the un-investigated and discovering a hidden world of the simple.

The man who mistook his wife for a hat is a musician professor who becomes unable to recognize faces and define objects in accordance with their shape, unless they possess a very distinctive single feature. Images does not integrate in whole, inter-relational, bigger landscapes, but remain isolated objects that often interchange their conventional, logical positions. The whole outside world is sustained by the inner music that fuels the capacity of accomplishing daily tasks. When the inner music stops, so does his coherence with mundane activities. 

The disembodied woman is a young woman whose sudden collapse of feeling her own body, makes impossible the coordination of her body parts and whirls them in a chaotic, out of control play. Her attempts of grabbing or holding things fail, as hands lack motion acuity and seem to have their own will. Her feet feel unsteady on the ground. She ceases to feel her body like her own, she feels disembodied. Struggling to compensate for the loss of her proprioception system, she is able to coordinate her members again only by visual concentration. 

The eyes right woman has lost her “left” consciousness, after the right cerebral hemisphere was severely affected by a stroke. The left visual field is dark, she can not look left, she can not turn left, she regularly forgets to make-up her left-sided face, she can not rotate her plate towards left. All her instinctive impulses, her attention, her natural movements are exclusively to the right. If she wants to finish up her meals, she has to rotate herself towards right until the left side of the plate come into sight. 

An ordinary day in the home ward. A group of aphasia-diagnosed are watching the President’s speech on TV. The speech is accompanied by frequent bursts of laugh. The nature of compensation is showing off. Their idiocy in understanding words has boosted their receptiveness of decrypting the rich spectrum of non-verbal messages: voice tone, intonation, fluctuations and emphasis, all visual cues. The inauthenticity of the speech stimulates their amusement. It’s a show of false gestures and intonations, of ridiculously emphasized tones and grimaces. 
Watching this amused group, one would doubt their capacity of comprehending the speech. One would think the non-verbal language loses its authenticity if not associated with the meaning of words.
But then the speech is also watched by an agnosiac lady, who contrary to the aphasiacs, can not distinguish characteristics of voice (intonation, emotions) behind a spoken message. For her, words and relations between words stand out, unaffected by other   factors. Her analysis of the speech makes one doubt his/her own abilities of getting the right message. To her, the speech in itself was inconsistent and contradictory: “the speaker was either brain-damaged, either had something to conceal...”

Tourette’s syndrome becomes so embedded in one’s life that it becomes part of one’s personality. The uncontrollable seizures, the sometimes violent gestures and words make the Tourette’s patients easily recognizable. A cure for calming their inappropriate reactions would make some fear they would also loose essential personality traits. The improvised and spontaneous gestures can sometimes boost their performance in life. Should a cure threaten one’s consistency with his personality? 

The dog beneath the skin is the story of a young man who experiences extreme enhancement of olfactive senses. This peculiar transition to a primordially olfactive surrounding reality turns his values around. His power of concentration as well as his interests are changing, as he becomes enslaved by the force of smell. The reception of visual information falls on second place, as he now relies on a stronger perceptional input. Places, street corners, objects, humans receive a distinct character through their exclusive smell. The story reveals how the well proportioned human senses play a big role in the normality of life.

For some, the reality is not recognizable in the immediate surrounding experience. The actions which fuel the standard “normal” lives have no meaning and no attraction for them. They are commonly looked at and labeled as retarded, unadapted, antisocial creatures. But for some of them, the reality makes sense differently, taking various shapes: of numbers, of drawings, of music. For the calendar-readers twins, who seem to have mathematical algorithms natively imprinted in their brains, numbers are regarded as friends. Numbers are full of life, have distinct characters, are personified. For the musical encyclopedic retarded, music is the only thing that gives him coherent self-expression. For the autist artist, drawing is an act of communion with the outside world. 

Oliver Sacks takes each case and integrates it into normality. A normality that has no standardized forms, no prejudices, no concrete rules. A normality that expands to boundaries we might have never thought of.
The book is a good read for those who want to step inside the entangled and complex world of the brain, for those who want to step closer to the realization of what makes us humans. It is a book that opens new realities before us and makes us aware of how perfect functionally our brains can be.