Actually, it's not just a straight reprint. In fact there are changes as I suspected, it being a new Edition.
Here is the new Table of Contents:
Game Programming All-In-One (3rd Edition)In summary, the changes from the 2nd Edition appear to be as follows:
Chapter 10: Programming Tile-Based backgrounds with Scrolling
becomes...
Chapter 11: Programming Tile-Based Scrolling Backgrounds Using MappyAL
Chapter 13: Vertical Scrolling Arcade Games, and
Chapter 14: Horizontal Scrolling Platform Games
become...
Chapter 13: Creating a Tile-Based Scrolling Arcade Game
Chapter 18: Introduction to Artificial Intelligence
becomes...
Chapter 19: Enhancing your Gameplay with Artificial Intelligence
Chapter 19: The Mathematical Side of Games
becomes...
Chapter 18: Basic 3D Graphics Programming Using AllegroGL
New chapter:
Chapter 16: Multiplayer Programming Using TCP/IP Sockets