This is an absolutely outstanding book - passionate, original, and easily accessible. It's far better than Homer-Dixon's The Ingenuity Gap, which was in itself groundbreaking. Homer-Dixon has a striking ability to bring together diverse ideas and research into one larger and compelling theme. He is also one of the few people in the world who really grasps the complexities and dangers of the human predicament in its totality. Many readers won't like this book's argument - that some form of crisis in the future is now extremely likely, that we'd best get ready for it, and that (if we're lucky) it might ultimately produce some good - but after finishing this book I find these conclusions inescapable and largely correct.
The book is rich with new ideas, on practically every page. I do wish the author had given us more on how "open-source" architectures on the Internet could be the basis for new forms of democracy, and for mobilization of non-extremists, but clearly he's just beginning to work through these ideas.
If you want to know about the role of energy scarcity in the collapse of the Western Roman Empire, the sources of modern capitalism's unchallengeable obsession with economic growth, the causes of people's widespread denial of our global crisis, the relationship between rising complexity and social breakdown, or the real story on global income inequality - the list of subjects covered goes on and on - this book is unmatched. But don't expect that it won't challenge some of your preconceptions. The book is definitely not for intellectual sissies, nor for people whose minds are already made up.