Overall I found it to be a very good book, it explains settings and what they do represent. I'd been using VRay for over 2 years when I read it, so many things I already knew, but the book has shown me some things I didn't know, and also made some things more clear.
It also shows the post production side in photoshop to give the images that final extra something.
Only 1 thing bothered me, I expected to have both Vray and Mental Ray for both examples/projects that you work though in the book. But the interior is done with Mental Ray and exterior with Vray.
Though the principles may be the same no matter what you use, I was hoping that for each scene you would be shown both setups (Vray, Mental Ray).