The Ringworld Engineers by Larry Niven

RETURN TO THE RINGWORLD
It's been 20 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, it intends to regain its status by bringing back such extraordinary treasures from the Ringworld that its fellows will have to 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. His quest becomes
a wild and gripping venture,
blended with mysteries and spectacular technologies that only Niven can conjure!

Condition: Good. Wear and creasing.