Hawking is a terrific self-promoter, and he managed to grab a lot of headlines for this book by claiming he'd killed God or whatever, but the truth is there's very little in this book that Brian Greene didn't cover - and cover better - ten years ago. In fact, a lot of this is stuff Hawking himself has covered in A Brief History of Time.
In the last chapter he brings up Conway and Turing and things get significantly more interesting, but it's too late by that time, since Hawking apparently feels he can't publish a book of more than 200 pages. I felt like we were at the start of something interesting there; I would've liked to hear more about it.
In general, this confirms that I'm not a big fan of Hawking. He bills himself as "science explained for the masses," but he doesn't actually explain things all that well - or, at least, there are folks who can explain it better. And in trying to cover so much in his books, he ends up covering nothing well enough.