Siddhartha by Hermann Heese and Zen and the Art of Motorcycle Maintenance by Robert Pirsig. I have been returning to them every few years since my teens, especially the first, which I have read so often and in so many different translations that I practically have the story memorized. Of course Walden and Autobiography of a Yogi and Old Ben's autobiography, as you mention, though I don't think I've read those since I was in college. Also, pretty much anything by Alan Watts, but again I haven't reread much of his stuff since college.

I'll have to look for The Myth of Normal.