Ten years after Ringworld, and after having received many letters with feedback apparently mostly about the mathematical assumptions and implications of the construction of the Ringworld, Larry Niven revisits his best-known creation.

Almost thirty years after their original exploration of the Ringworld, Louis Wu and the Kzin Chmee are abducted by the recently deposed Hindmost and forced to go there again. They find the Ringworld knocked off-centre and about to collide with its sun. Louis embarks on a quest to try and prevent the catastrophe and learn more of Ringworld's secrets and its elusive builders. In the process he gets to know (quite often even in the biblical sense) a few of the various humanoid species that populate this most stunning artifact in known space.