I also bought this book at Siggraph 2007, and am very impressed with my purchase. This is a tasteful and extensive collection at a very reasonable price. Section titles include Fantasy, Characters, Scenes, Cartoon, and Sci-Fi images. Each of these broad categories contains about 15 sub-sections that each focus in on one specific art piece, with several pages of in-progress work and discussion by the artist. Sections vary in length from 4 to 6 pages. Some are even longer. There are a few more 3d works than 2d, but this distinction is hardly noticeable.
The supporting 3d images include clay renders, wireframes, scene screengrabs (with lights, alpha planes, and other techniques displayed), and sometimes UI screengrabs. Supporting 2d images include reference images used by the artist, pencil sketches, and sometimes idea development before actual production began.
Unlike many other books, the binding of the Digital Arts Masters is surprisingly hardy. It has heft. I feel comfortable reading it without worrying about pages detaching from the spine.
I would recommend this purchase to those looking for some inspiration and technique ideas. After feeling a little frustrated with Ballistic publishing, I'm glad I bought this book.