Some rather intriguing/thought-provoking philosophic texts with which I am familiar (and which I recommend) include the following: "The Will To Power" and "Beyond Good & Evil" (both by Friedrich Nietzsche), "Meditations" by Marcus Aurelius, "The Discourses" (and "The Prince") by Niccolo Machiavelli, "The Perennial Philosophy", "The Doors of Perception", and "Heaven & Hell" (all three by Aldous Huxley), and "On The Soul" by Aristotle.