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This book surprised me. I thought its main gimmick would be the "Ringworld" concept, and as such I thought it wouldn't have much substance to it. Surprisingly, it contained a huge amount of worldbuilding (no joke intended) and character development. Many of the 'sci-fi' concepts dreamed up by Niven were fascinating to ponder. The book takes an odd, non-sci-fi turn near the end. I hate to give anything away, but I read "Mostly Harmless" by Douglas Adams immediately after and I found some incredible similarities with his concept of "temporal reverse engineering". I enjoyed the book, although I fear my reading was a little hindered by the quality of the audiobook I listened to. I would give it 3 stars for that, but I cannot blame the author for the fault of the medium. I look forward to reading the rest of the books in the series.