It isn't all quantum physics. He throws in a lot of information about elementary particles, strong and weak nuclear force, the big bang, and finishes off with aliens. His style of constantly relating unfamiliar things back to the familiar really makes this book easy to read, and not get totally lost in like many popular physics books. Additionally the fact that each chapter stands alone means there's less chance of getting stuck on a concept and having to give up. It is written at a level that anyone with a high school physics education could read it (I think), but there were only a couple times where I felt irritated by unnecessary levels of detail. If you've got a degree in astronomy or particle physics, this would probably be boring, but I really felt like I learned something. There wasn't a lot that I hadn't seen before, but it was put together in a way that was interesting, and helped me make a lot of new connections.
So, if you like popular physics books, I think you'll love this one. If you're scared of popular physics books, you'll probably still really enjoy it. Chown manages to simplify some really difficult concepts without oversimplifying, and communicate them in a really engaging way. I definitely want to acquire a copy of this book if only to lend it around to everyone.