The White Box Essays by Jeremy Holcomb isn't just a book about game design, but rather an overview of the whole process. Each step of creating a game is covered by a short chapter. The topics aren't covered in great depth, but do provide valuable information. If you want to read 5 pages about what a game "is", check out a book like "Rules of Play"... if you want information about nearly every aspect of creating a game, from conception to production to fulfillment, then the White Box Essays is the place to start.
Thoughts and general ramblings about many things, mostly games...