I'd have to go with Louise L. Hay's "You Can Heal Your Life". It's an oldie, and to someone who hangs out reading Steve Pavlina, there's probably not much "surprising" in Hay's book, but it really revolutionized my life at the time since I'd had no other exposure to any kind of self-development stuff.
Anyway, I found Hay's book as a preteen. At a public library while looking for books on psychic power-- I wanted to learn telekinesis
I never did learn telekinesis, but it was worth it to find out about positive affirmations and all the other stuff in YCHYL!