I recently purchased a copy of Half-Life 2: Raising the Bar from my favorite online retail outlet, Amazon. The book takes a behind-the-scenes look at the artistic development of the game, including a number of things that were cut from the final product. At 288 pages, it provides a great glimpse of the game-making process, especially as far as art direction is concerned. I've only read a tiny fraction of the book, but so far it's been enjoyable ... a highly recommended read.
In the online world, Garry's Mod for Half-Life 2 has resulted in some great online comics. My favorite is without a doubt Concerned, a strip that follows the "Half-Life and Death of Gordon Frohman." The writing is excellent, the visuals are top-notch, and the entire strip is hilarious. You have to start from the beginning to fully appreciate the strip. Anyone who has played the game will certainly get a kick out of it. New comics are posted every Monday, Wednesday, and Friday. As such, I've added it to my weekly online funnies list (which includes the likes of Ctrl+Alt+Del, Penny Arcade!, and The Joy of Tech). Some other good Half-Life related strips can be found at PHW Online. It's great to see such clever use of gaming technology.