I recently reread this and it's still delightful after all these years. Niven is so much fun because of his fascinating ideas, and the playfulness with which he approaches them. The ringworld is a beautiful work of art, technology, and imagination. Ditto time stasis fields, mirrored focusing sunflowers, using generated gravity as an art form, hurricanes shaped like giant human eyes. Even more fun are the glories of the Puppeteer home planets flying to the edge of the galaxy in a kemplerer rosette... stepping disks, mile high skyscrapers, and the planetary problems of waste heat. I love Puppeteers and Pak Protectors, Kzin, Outsiders, and Gummidgy Reachers. Niven lets us revel in this glorious xenophilia that he has. His aliens are delightfully non-human.
I did find myself surprised by how sexist many of the underlying assumptions were, which I don't remember thinking the first few times I read these books back in the 70s. I guess that shows we are making some kind of progress in our society. =)
It's interesting from a history-of-science perspective as well. Back in the 1970s, room temperature superconductors seemed a lot more technologically advanced than they do now, and the idea of Lewis Wu clacking away on a typewriter in college circa 2200 is laughable. It reminds me of Heinlein's "The Rolling Stones" from the 1940s which had the Stone family calculating interplanetary orbits on their slide rules. =) I love thinking of how ludicrous some of our own ideas of the future will seem in 30 more years.
This and Protector are my two favorite Niven books. I find Niven alone to be far superior to the Niven-Pournelle collaborations that came later.