You can see some pages of the book on the official site: http://www.starwars.com/episode-iv/bts/article/f20070220/index.html?page=1
And there's a preview on the publisher site: http://www.randomhouse.com/catalog/display.pperl?isbn=9780345494764&ref=news&name=starwars0507
Don't hesitate to buy it blindly ! It's the best book ever published on Star Wars. (and get the hardcover version, if you like storyboards, there's a lot of them in the extra pages)