• "The Unconscious as Infinite Sets" by Ignacio Matte Blanco. Reformulates Freud in logico-mathematical terms and establishes a formal system (bi-logic) to describe unconsciousness phenomena: in case you ever wanted to apply category theory to study yourself.
• "The Protracted Game" by Scott Boorman. Interprets Maoist's revolutionary strategies during 1927 - 1949 period as a game of Go. Interesting both from historical, military, and game-theoretical perspective; raised an appreciation of Eastern wisdom and 'board games as a tool of thought' [2] for me.
• "The Unwritten Laws of Engineering" by W. J. King. Written in 1944, but the advice is still relevant, more so to the software engineering field. Should be at least skimmed at any part of your career.
• "The Myth of Sisyphus" by Alber Camus. Unequivocally answers the most important question there is — does life have meaning, and if not, should you kill yourself over it? I read it in my teens while wrestling with existential dread, and lived a somewhat happy and interesting life ever after.
[1]: http://homepages.math.uic.edu/~kauffman/Form.html
[2]: There's also "Laws of the Game" by Eigen & Winkler that describes natural phenomena as glass-bead games with various rules.