Since the first creatures existed on planet Earth there have apparently been five mass extinctions, some of which were caused by us humans, some by other environmental disasters, such as asteroid impact. This book is about some of those extinctions, and the massive changes the planet is going through due to our actions, and making some predictions about what could happen next.
Kolbert makes a pretty compelling case that the sixth extinction in question could be us, caused by us. Oh, but the Earth could be repopulated by giant rats. Just as the avian dinosaurs managed to withstand the asteroid impact, the rats may well withstand whatever ruination we bring on the planet.
Kolbert touches on biology, geology, botany and various other natural history related subjects and she manages to explain them all in terminology that I can understand. The situation certainly looks very alarming, but her style is not over dramatic. She tells stories of species that have gone extinct, and species that are well on their way due to our activities. She explains how the various species interact with others and speculates how each of their extinctions can affect the rest of the ecosystem of the planet.
The actions of previous humans has, as Kolbert points out, resulted in some humans desperate enough to put their arm up the bottom of a rhino to give her an ultrasound and to give rare crow species a handjob. It is not just doom and gloom, though. There are lots of fascinating natural history facts, about past and present species, including us humans and our fellow apes.