Some of my favorites for Game Design as a discipline and craft.

MDA: A Formal Approach to Game Design and Game Research, Robin Hunicke, Mark LeBlanc and Robert Zubek.

Fundamentals of Game Design, Ernest Adams and Andrew Rollings.

Rules of Play: Game Design Fundamentals, Katie Salen and Eric Zimmerman.

Game Design Workshop, Tracy Fullerton

A Theory of Fun, Raph Koster.

Creating Emotion in Games: The Craft and Art of Emotioneering, David Freeman.

Chris Crawford on Interactive Storytelling, Crawford, Chris.