The Art of Game Design, by Jesse Schell

Consciousness Explained, by Daniel C. Dennett

Contingency, Irony, and Solidarity, by Richard Rorty

Darwin's Dangerous Idea, by Daniel C. Dennett

Finite and Infinite Games, by James P. Carse

I Am a Strange Loop, by Douglas Hofstadter

A New Kind of Science, by Stephen Wolfram

Peace Is Every Step, by Thích Nhất Hạnh

Philosophy and the Mirror of Nature, by Richard Rorty

Self-Reliance, by Ralph Waldo Emerson

The Selfish Gene, by Richard Dawkins

Freedom Evolves, by Daniel C. Dennett

Game Mechanics: Advanced Game Design, by Ernest Adams and Joris Dormans

Religion and Nothingness, by Keiji Nishitani

The Self-Overcoming of Nihilism, by Keiji Nishitani

The 7 Secrets of the Prolific, by Hillary Rettig

• Challenges for Game Designers, by Brenda Brathwaite and Ian Schreiber
• The Complete Guide to Asperger's Syndrome, by Tony Attwood
• The Elegant Universe, by Brian Greene
• The Fabric of the Cosmos, by Brian Greene
• Game Design Workshop, by Tracy Fullerton
• How to Fail at Almost Everything and Still Win Big, by Scott Adams
• Lauren Ipsum, by Carlos Bueno
• The Nordic Theory of Everything: In Search of a Better Life, by Anu Partanen
• Procedural Generation in Game Design, edited by Tanya X. Short and Tarn Adams
• A Theory of Fun for Game Design, by Raph Koster
• Uniquely Human, by Barry M. Prizant, PhD

Books in this list might very well get moved to one of the three tiers above. But first I need to re-read them, since I've generally only read each of them once, and that one time was quite a while ago. As such, I neither remember clearly what I thought after reading them, nor did I have a very good foundation for critique at that younger age to really make any definite determinations of their worth to me. Especially the philosophy books, as my personal philosophical views have undergone multiple reconstructions, and I'm unsure of what I'll think today of those books that were highly influential on my thought over a decade ago. But to be on this list, I at least need to have a strong suspicion that a second reading would be valuable, reflecting the worth that the books likely hold for me.

• Flatland, by Edwin A. Abbott
• Quantum Physics and Experience, by David Z Albert
• On Liberty, by John Stuart Mill
• A Treatise of Human Nature, by David Hume
• An Enquiry Concerning Human Understanding, by David Hume
• The Religious Case Against Belief, by James P. Carse
• The Blind Watchmaker, by Richard Dawkins
• Breaking the Spell, by Daniel C. Dennett
• The Problems of Philosophy, by Bertrand Russell
• Russell on Religion, by Bertrand Russell
• The Conquest of Happiness, by Bertrand Russell
• Religion and Science, by Bertrand Russell
• Marriage and Morals, by Bertrand Russell
• How We Think, by John Dewey
• Thus Spoke Zarathustra, by Friedrich Nietzsche
• The Varieties of Religious Experience, by William James
• What Is Time?, by G. J. Whitrow
• About Time, by Paul Davies
• Chaos Theory Tamed, by Garnett P. Williams
• Choosing Children, by Jonathan Glover
• Prisoner's Dilemma, by William Poundstone