Siddhartha by Hermann Hesse
A young man, blessed with loving parents and a safe home in a world where want and neglect abound, leaves this haven in search of himself. He joins the Samanas, a band of wandering ascetics without possessions or earthly ties. His quest unfulfilled, he descends into a life of unbounded luxury and indulgence. Where is truth? Where will his soul find true ease? In denial? In decadence? Or in some truth far greater than himself, so simple, so close to him, yet so obvious that only clear eyes may see it?” -Audible
I believe I added this book to my list because Tim Ferriss mentioned it several times in his podcast. In one of the more recent ones, he said that many of the people featured in Tools of Titans actually mentioned this book as well. Again, I cannot refuse a highly recommended book by so many esteemed people.