Complex sentence: The book demonstrates that the Earth is in the midst of a modern, man-made, sixth extinction n the book, Kolbert chronicles previous mass extinction events, and compares them to the accelerated, widespread extinctions during our present time.
Split into simpler sentences: The book demonstrates that the Earth is in the midst of a modern, man-made, sixth mass extinction. In the book, Kolbert chronicles previous mass extinction events, and compares them to the accelerated, widespread extinctions during our present time.