Book excerpt: *Unprecedented access behindHalf-LifeandHalf-Life 2 *A forward by Valve founder Gabe Newell *Hundreds of art, design, preproduction, and other art pieces crammed into the book *Over a dozen key members of Valve's staff interviewed *Officially approved by Valve *Behind City 17 and other locations *The development of the Source engine *A rogue's gallery of beasts, characters, and monstrosities *Key weapons development revelations *A tour of many of the game's locations, from inception to completion *Filled with art, screens, and anecdotes from the Valve team