I got the book today and it's pretty neat. You can kind of gauge where in production the book was written based on what it includes, and it actually seems to cover most of the movie as we ended up seeing it on-screen. I haven't gone page by page through it, but one notable omission is
Spoiler
the Predator Killer nano-suit
but I'm not surprised by that. From my brief glance through it, it looks like all the character deaths featured are the same.
The concept art is neat, and there's some annotations regarding why certain design choices were made. There are a bunch of really high quality close-up photos of the Fugitive Predator's gear, a deck plan of his ship, CGI models for the Preda-dogs, all kinds of stuff.
I'm a sucker for movie concept art books as a way to get a glimpse at the evolving design process; generally the movie doesn't even have to be that good as long as it's visually interesting. I've got the art books for AvP and Terminator Salvation, and they're both full of really neat stuff.