Spaw I'm just coming to this thread and you already beat me to my selection. Possibly not the best books I ever read, but that ones that had the most impact on me when I was young, Simone de Bouvoir's The Second Sex and To Kill A Mocking.

I had to do an oral book report in a Junior Highschool class years ago, which due to my shyness was usually a painful experience. During the report, the usually restive class gradually became silent, to add to my embarrassment. When I finished, the English teacher looked at me sternly and in an accusitory tone said. "Susan! I don't believe you read that book!" as I started to crumble inside, he continued sofening his tone and added "You lived it."