For artbooks, the most professional (and therefore most expensive) are made by Ballistic Publishing, who specialize in high-end compilations of digital paintings and tutorials. All of their books are probably worth obtaining, but they are based in Australia, which makes it extremely expensive to get their more limited edition books (paperbacks are available at Amazon for more reasonable prices):
http://www.ballisticpublishing.com/
Game-related Ballistic Artbooks (Art of the Game Series)
The Art of God of War 3 (Softcover, Hardcover, Special Edition Leatherbound, and Folio Edition*)
The Art of Gran Turismo 5 (Softcover available for preorder on Amazon, other editions unknown)
The Art of Oddworld Inhabitants (Softcover, Hardcover, Limited Edition Leatherbound, Folio Edition)
The Art of Twisted Metal (Softcover available for preorder on Amazon, other editions unknown)
The Art of Uncharted 2 (Softcover, Limited Edition Leatherbound, and Folio Edition)
*Note: Folio Editions are their most exclusive and collectible versions, limited to ~100-300 copies and priced at about $200-400.