I’d recommend The Bhagavad Gita. You don’t have to be of the Hindu faith to get something out of it, it’s enough just to see it as a different way to view things.
My favorite translation is by Ranchor Prime, because his version is organized into parables instead of a line-by-line analysis, but there is also a nice public domain version at Project Gutenberg, HERE.
My wife reminded me that The Answer Is… Reflections on My Life by Alex Trebek is really good, too.