In 1985 I read a book. I was then a freshly employed software engineer in a world where computers were fantastically efficient calculators and I had nearly given up hope trying to convince people that it was important to study and understand how human brains worked if you wanted to make these computer things better. This book taught me that brains are WAY weirder than we think they are and that people who parade around pretending they actually understand these brain things are in fact full of it.
I can't say that The Man Who Mistook His Wife for a Hat changed my life so much as it opened my eyes to how vast the horizons of discovery and opportunities for learning could be, right inside our own heads.
In 1995 (or thereabouts - I can't remember the exact date) I first saw Sacks speak live, at a Media Lab event. I've never before or since seen someone so effectively call bullshit on Nicholas Negroponte. Of course, Sacks was too polite to use that word but that's what he was doing. The two have been friends for a long time and Sacks grinned like a madman throughout the exchange, amused at his friend's discomfort.
The world is a better place for what Sacks has done in his 80+ years and it will be a worse place when he is gone.