There's a lot of different artistic style in the book. When Brad Bird came to Pixar, he brought with him his team of artists, those that had worked with him on The Iron Giant.
Each artist produced concept art using different materials and style. There are collage, gouache, digital, marker, acrylic and pastel. Each drawing generates ideas and inspiration. You'll have no idea the movie was created for art so varied. There are no rendered stills from the movie.
The book touches mainly on character design and artistic direction of the movie.
If you want the process of creating The Incredibles, you'll want to grab the DVD instead. There are pretty comprehensive behind the scenes included in the DVD.
There are more pictures on my blog. Just visit my Amazon profile for the link.