On the Road by Jack Kerouac – I learned about the Beat Generation, a group I never knew existed, and about a lifestyle that dominated my thinking as a young adult.
The Adventures of Huckleberry Finn by Mark Twain – The best novel of American literature ever written.
QB VII by Leon Uris – The first adult book I ever read (as a 7th grader).
I Never Loved Your Mind and My Darling, My Hamburger both by Paul Zindel – I am not embarrassed to admit that these were the first books to make me cry at the end. They also turned me onto YA novels as a genre.