1) 1984 by Orwell was a pivot point back in school

2) The Power of Now by Tolle gave me a path to set towards

3) Democracy by Hoppe made me understand why government by force sucks balls

4) Siddharta by Hesse is just beautifully written

Honourable mentions: 21 Lessons by Gigi, Doors of perception by Huxley and Die Welt von Gestern by Stefan Zweig