The Book Siddartha is the book of the Buddha. If you aren't at all open to any thing Buddhist, than I don't reccomend it, as it is a spiritual book. I am not particularly Buddhist, but the book was such an enlightening journey that I believe any NF, regardless of faith can gain some englightenment from it, as well.
It's the story of seeking self truth. Destruction of the ego, destorying the self. How it always dynamic. How we can learn from those most opposite us. For instance, the Buddha meets a selfish upper class princess who despices the Buddha because he is a wanderer and has poor clothes and no pocessions on. He is drawn to her because she has what he lacks. She serves as his teacher and he learns from her. This aspect of learning from others what you don't have, even if it is not what you seek, is a wise decision.
This book really meant something to me. I really really reccoment it. Please don't judge it because it is of Buddhist teachings. Gain some depth and overlook this aspect. I can find that it can talk to all of us, regardless of faith.