Back matter

Marshall B. Rosenberg, Nonviolent Communication: A Language of Life: The source of the whole mindset: needs, feelings, strategies, OFNR, power over and power with, and why rewards and punishments fail. If you read one thing from this list, read this. I learned it through videos and audiobooks, which work just as well. Used throughout, above all in Chapter 9.
The Center for Nonviolent Communication, cnvc.org: Free material, including the needs inventory and the feelings inventory. Search for "NVC needs inventory" and "NVC feelings inventory", and print both (The lists to keep at hand).
Manfred Max-Neef, Human Scale Development: The economist's view of fundamental human needs, and the matrix of needs as qualities, things, actions and settings. Also the one economics idea the book keeps (Chapter 9, Chapter 17).
William Glasser, Choice Theory: Another route to the same conclusion: all behavior is an attempt to meet basic needs, and fun is tied to learning. A bit reductive, but a clear second angle (Another angle: Glasser).

Rewards, motivation and competition#

Alfie Kohn, Punished by Rewards: Why extrinsic goals and incentives poison whatever they're attached to. Kohn writes about schools, workplaces and families, and every word applies to game design and game development (Chapter 6, Chapter 9).
Alfie Kohn, No Contest: The Case Against Competition: Competition isn't a law of nature; it's an arrangement people invented. This book made me stop playing competitive human-vs-human games for good, and I recommend it to every game designer (Chapter 15, Chapter 30).

Marketing and business#

Tad Hargrave, Marketing for Hippies (marketingforhippies.com): Marketing and business in a way that doesn't make you hate yourself. Not from the games industry, but easy to adapt, and most of it is free (Marketing).

The four stages of competence, usually credited to Noel Burch: why intention runs ahead of skill, and how to skip the first stage (Chapter 14).
Murphy's law: "Anything that can go wrong, will go wrong", and at the scale of a playerbase it's guaranteed (Chapter 14).
Carl Sagan, Cosmos: "If you wish to make an apple pie from scratch, you must first invent the universe" (Chapter 21).
Elisabeth Kübler-Ross, On Death and Dying: the five stages of grief, which people go through when a new idea shakes their world (Chapter 33).
Jacque Fresco, "nothing things" (the talk, and his whole playlist): things that fill a life without giving anything back. Most relevant to games that violate the need for meaning (Needs at a Glance).
Cognitive biases: there are well over a hundred named ones, and you don't need to learn them all. They share one root: believing without verifying (Chapter 4).

Much of Parts II, IV and V started as my articles, which are free on the portfolio site. They're blunter than the book, and they have pictures.