I just got my complimentary copy of Art Direction Explained, At Last!
by Steven Heller and Veronique Vienne. I just cracked it, so I'll spare you the long winded review, but I like what I've seen so far. The Illustrator's Guide To Art Direction
by Christoph Niemann and Nicholas Blechman, Glossary
by Peter Buchanan-Smith and Laurie Rosenwald's great piece art directors i have known, loved, respected and reviled
are each worth the cover price alone.
I have a piece in there, but don't let that scare you off - the rest of the book more than makes up for it.
Here's one of my spreads: