Larry Niven – Ringworld

Pierson's puppeteers, strange, three-legged, two-headed aliens, have discovered an immense structure in a hitherto unexplored part of the universe. Frightened of meeting the builders of such a structure, the puppeteers set about assembling a team consisting of two humans, a puppeteer and a kzin, an alien not unlike an eight-foot-tall, red-furred cat, to explore it. The artefact is a vast circular ribbon of matter, some 180 million miles across, with a sun at its centre - the Ringworld. But the expedition goes disastrously wrong when the ship crashlands and its motley crew faces a trek across thousands of miles of the Ringworld's surface.

It's been twenty years since the quixotic and worldsweary Louis Wu discovered the Ringworld. Now he and Speaker-To-Animals are going back, captives of the Hindmost, a deposed puppeteer leader. With Louis' help, the Hindmost intends to regain his status by bringing back such extraordinary treasures from the Ringworld that his fellow puppeteers will have to be impressed. But when they arrive, Louis discovers that the Ringworld is no longer stable ...and will destroy itself within months. To survive he must locate the control center of the legendary engineers who built the planet.

The human, Louis Wu; the puppeteer known as the Hindmost; Acolyte, son of the Kzin called Chmeee . . . legendary beings brought together once again in the defense of the Ringworld. Something is going on with the Protectors. Incoming spacecraft are being destroyed before they can reach the Ringworld. Vampires are massing. And the Ghouls have their own agenda--if anyone dares approach them to learn.
Each race on the Ringworld has always had its own Protector. Now it looks as if the Ringworld itself needs a Protector. But who will sit on the Ringworld Throne?

Explorer Louis Wu, an Earth-born human who was part of the first expedition to Ringworld, becomes enmeshed in interplanetary and interspecies intrigue as war, and a powerful new weapon, threaten to tear the Ringworld apart forever. Now, the future of Ringworld lies in the actions of its children: Tunesmith, the Ghould protector; Acolyte, the exiled son of Speaker-to-Animals, and Wembleth, a strange Ringworld native with a mysterious past. All must play a dangerous in order to save Ringworld's population, and the stability of Ringworld itself.