Well, if you really don't care about what becomes of your brain:
http://en.wikipedia.org/wiki/Codex_Seraphinianus
edited 24th Sep '12 10:33:36 AM by Jhimmibhob
I'm far from an expert on art books, but I feel like pimping The Art of Discworld by Terry Pratchett and Paul Kidby. It has some very good art in it.
I'm personally fond of Lady Cottington's Pressed Fairy Book
. Terry Jones (Yes, the Monty Python Terry Jones) wrote it and Brian Froud (Yes, the Brian Froud who designed both The Dark Crystal and Labyrinth) illustrated it. It's sick, twisted, delightfully macabre and absolutely gorgeous, in a sick, twisted, and macabre way.
edited 24th Sep '12 5:00:43 PM by Madrugada
Check out the works of Graeme Base (I think that's how you spell it). The Eleventh Hour and Sign of the Seahorse. Bonus: Both books include incentive to pour over the art intently, as they contain hidden-object-style puzzles where you search the pictures for hidden clues.
"Proto-Indo-European makes the damnedest words related. It's great. It's the Kevin Bacon of etymology." ~MadrugadaGames Workshop published a series of books collecting the art from Sabretooth's Horus Heresy card game. Horus Heresy: Collected Visions
is rather obviously all four books in one volume, and it's a gorgeous thing to look at. Well, if you like that sort of thing, that is. :)
I'm also a big fan of Chris Foss' sci fi art. Hardware: The Definitive SF Works of Chris Foss
is another lovely thing.
Books from the La vie secrete des betes series (published in English as Nature's Hidden World) have some great illustrations, especially these illustrated almost photorealistically by Carl Brenders
.
edited 25th Sep '12 4:15:36 AM by Korodzik

I love books filled with fantastical art. Books like the Dinotopia series, Wayne Douglas Barlowe's Expedition, The Wildlife of Star Wars, Robota by Doug Chaing and World of Kong: A Natural History of Skull Island.
Any other suggestions?
A fistful of me.