After more than four decades, the fate of the Ringworld and its cast of trillions is revealed. Niven and Lerner have outdone themselves in bringing to a conclusion the saga of a world vast and diverse beyond measuring. And the ultimate danger comes from an unexpected front.

Robinson, already famous for his Mars and Environment Trilogies, tackles the questions of returning to a degraded environment on Earth after the human species has been living in space habitats and colonies around the solar system for several centuries.