Great question. It's the main reason I read anything at all. I'd say in rough order of influence and importance to me:
An Autobiography: The Story of My Experiments with Truth,
Satyagraha in South Africa, and most other writings by Mohandis K. Gandhi
Demian and
Siddhartha by Hermann Hesse
The Razor's Edge by W. Somerset Maugham
The Hero with a Thousand Faces and other books by Joseph Campbell
Unto This Last by John Ruskin
The Autobiography of Martin Luther King, Jr. by Clayborne Carson
The Ascent of Man by Jacob Bronowski
Benjamin Franklin by Carl Van Doren
Slaughterhouse Five by Kurt Vonnnegut
Lying Awake by Mark Salzman
The God of Small Things by Arundhati Roy
Sorry for listing so many. And I have so much more to read that I hope will be of equal importance to me.