For those who haven't heard-
Valve will release the source for Half Life 2(as they did for HL1).
Prima is publishing a book on coding mods for the game(or it explains the source code).
Anyways, there will also be a book published that shows what went on during the making of the game. You guys should check them out(Amazon "Raising the Bar")
The RTB book comes out Thursday, and the coding one will be out December 14
Raising the Bar