Search Inside Yourself - Chade-Meng Tan
Bible - several authors
Siddhartha - Hermann Hesse
Fight Club - Chuck Palahniuk
Eléments de Philosophie Angélique - Denis Marquet (french)
Au coeur de l'instant - Jean Bouchart d'Orval (french)
At some point in my life, while I was going through severe depression, I got interested (by the folks on HN) into looking more into Buddhist philosophy and meditation. This little book, quick to read, made me realize that our selves are not what we think they are, and that our emotions are impermanent, that we can deal with them by simply acknowledging them instead of letting them overthrow us. It's a brilliant simple idea, though it is harder to put into practice. (I am still not quite managing to be a regular meditator to this day)
This little book changed my life, and I've now bought it or lent it to several people from my friends or family in the hope that it may have the same impact on them as it had on me.