Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Not up to the standards of his other works

Niven must have been hungry. How else to explain a ringworld creation which was nowhere near the enlightened excitment of his other works in the series. The last third of the book has nothing to do with the first two-thirds. Skip this one and read his other works. He's still one of the best. (But even Michael Jordan shoots an air-ball occassionally.)