First and most important, this book will change the way you think about the American prairie. I live here at the edge of the prairie near Indianapolis, and there are a few spots maintained as native prairie. Manning isn't talking about these little islands but about a huge, free ecosystem and the horrors that we have inflicted upon it and its fauna and flora. I confess that the image of grizzlies chasing elk calves across the grassland is beguiling, and illustrates what we are missing. He makes a persuasive case that we need lots and lots and lots of grassland, maintained as such. Manning has a good story-telling sense, and a good eye for explaining the grassland. You will not look at the prairie in the same way again.
There are some nicely provocative bits. His vision of the prairie rests on bison ranching, with the animals eating native grasses without irrigation, fertilizer, or other capitalist agriculture. As if that's not controversial enough, he makes a serious case that a meat-and-leather prairie economy rests easier on the land than food crops such as wheat or corn. These crops have destroyed the prairie and harm the broader environment because of the extensive irrigation and fertilization required. Obviously, this strategy of making our agriculture conform to the land instead of forcing the land to conform to our agriculture would be a major change for Americans and others around the world..
Manning is not afraid to take the next logical step, and he makes a principled argument against vegetarianism. Eating free-range bison raised on natural grasslands, he argues, would sit more lightly on the ground and would probably use less (petroleum-based) energy. This is not your conventional environmentalist, to say the least.
Despite those strengths, the book is weakened by a modest number of trivial errors of fact. These come in sidebar comments about irrelevant matters and have nothing to do with grassland, so I'd rather not list them here. They did make me question the accuracy of his reporting on grassland, though. I wouldn't rely on this book as your sole source of facts, but Manning's vision and wonderful writing make it an invaluable book nonetheless.