Mine was probably non-fiction; Rhian Malan's MY TRAITOR'S HEART. Set in South Africa's Apartheid and written by a white SA journalist. It was an utter revelation about the country and its people as well as the human propensity to judge and be fearful and forgive and eventually find a way out of racism.
I'd be interested to know what books, fiction or otherwise had changed others lives, perspectives, ways of living?