The Sixth Extinction is a collection of short studies of a particular species or ecosystem, and what is happening to it now. The net effect is a whole that is larger than the sum of its parts. Set against the backdrop of the first few chapters, which describe the causes and results of history's first 5 major extinction events (one of which killed off the dinosaurs), the author convincingly makes the case, based on well-researched data, that we are now experiencing the 6th major extinction event, the cause is us, and it began back when modern humans first evolved and began hunting the now-extinct Ice Age megafauna. But this isn't a dry, scientific study -- it's aimed at a layperson audience and is written as anecdotes about the author's travels to visit each species or ecosystem about which she writes. There are interesting characters and stories at each stop. Highly recommended for anyone, not just science enthusiasts.