I'm game.
I'm currently reading "Don't Make Me Think: Revised Edition" by Steve Krug. The book is primarily about website design, but anyone with half a brain could translate the design principles and main ideas into a game development context. I just finished Chapter 10(?) all about designing usability tests and how to get a feel for where the main issues are with your design.
After that, I've got "Design is Storytelling" by Ellen Lupton and "The Animator's Survival Kit" by Richard Williams queued up.