The book starts with a pretty good overview of relativity and black holes, which was good but I have heard most of it before. That doesn't mean I understand it, but I can get by. Then Greene moves to quantum physics. I had heard much of this before, and he provides an excellent and thorough explanation of it. I understood it much better than other explanations I've read -- which is to say, almost not at all, but that's not his fault. Quantum physics is simply too weird for words. Then Greene switches to his own apparent forte -- string theory. This was something I hadn't heard much about, besides the name. It's as bizarre as quantum physics and just as interesting.

There is plenty of history as well. The book is well written overall. Recommended for anyone who likes this kind of thing, and who has at least a basic familiarity of Einstein's theories of relativity. The book assumes you already know a little about them, but if you don't, you can always rewind a lot (I did).