Award-winning author Tim Flannery begins his epic history of our continent with an asteroid explosion 65 million years ago and ends it with sensible prognostications about North America 1,000 years hence. Between those points, his 368-page narrative unfolds with the jaunty ease of a Charles Kuralt Sunday morning chat. Flannery, who is a museum director, knows how to spice up his exhibits: He explains how to kill (and preserve) a mastodon; why North America was settled so late (40,000 years after even Australia) and why all radiocarbon dates are wrong.