Part II
The Mindset
This part is about the mental side of design: how to think, relate and decide while working on a project. On its own, it's the most important part of this book. The technical side that comes later is useless without it.
It starts with purpose, the reason anything in a project exists at all. Then it goes where purpose comes from, which means understanding human beings, their needs and their feelings, and what "fun" really is. From there it shows how to turn an inspiration into a clear purpose, how to choose between making a game and making an interactive tool, and how to use the purpose as a compass for every decision you'll ever make in a project.
Things get a bit heavy here, since this is where human psychology and human nature come in. It's necessary. Games are played by humans, and to make compelling games for humans, you have to understand humans. You're one yourself, so you already have everything you need to check what I say against your own experience. Please do.
Reactorcore
Game Design Technology: The Holy Grail of Fun