I admit it: physics makes my eyes glaze over. I'm not a dumb person. I was great at math in school, I wasn't intimidated by chemistry, I got a PhD, I taught stats, I programmed computers in a molecular biology lab at NIH, and physics does me in every time. I keep trying though, and this was one of my more successful attempts, which is why I give the book 4 starts. The fact that my eyes still glazed some is why it isn't 5.
Hawking makes some fairly sophisticated physics mostly pretty comprehensible using analogies and a decent amount of repetition of key concepts. I did this on audio, so there may have been illustrations that helped in the book format, but at times I still had a hard time picturing where things were going when he was describing more than 3 dimensions or tackling things like imaginary space/time or string theory. Still, I have walked away from this book many steps further down the road toward physics making sense to me than I was when I started. I think if I read or listened to it again, I'd be several steps more.
One thing that really helps is Hawking's sense of humor. Amid the dense science there are amusing anecdotes and funny little off-hand comments that lighten things. He also manages not to be too full of himself, which is impressive, given how much he has to be full of himself about.
What I don't know, given my tendency to glaze over when I read physics information in the science section of the New York Times, is how dated the science in this book has become since it was written. One thing that is clear from the book is that until scientists figure out a unified theory that brings all the observations physicists have made together, there are going to be more overhauls that take the accepted best theories of the day and either toss them out completely, or rework them a bit (and maybe resurrect some old ones from a new perspective). Given that, I can say that I think I'm making progress understanding where physics was at the point that this book was written, and I'm really hoping that any major new discoveries can be explained by Hawking in an equally accessible form down the road.