The ringworld and known space franchises are two of the best conceived ideas in the history of science fiction. "Ringworld" and "The Ringworld Engineers" are both a joy to read, whereas "The Ringworld Throne" is most definitely not. Fortunately, Larry Niven is back on form with the fourth (and possibly final?) ringworld book. "Ringworlds Children" continues louis wu's adventures aboard the enormous artificial ringworld and also fills in plenty of missing gaps about it's builders, the pak protectors - mankind's forefathers. The ringworld is under threat from other space-faring species, who all want to harvest the technology on offer without consideration for the effect on the billions of mankind-evolved inhabitants. Louis joins forces with the ghoul-people protector tunesmith and a newly-discovered protector, the only surviving member of the original pak who built the ringworld. Niven brings his incredible imagination to bear on the story, which is told in a far easier and involving manner than "The Ringworld Throne", and delivers an astonishing finale which had me re-reading it to make sure I'd read it right! Larry Niven, when he's of a mind, can deliver a story of pure hard science fiction wonder, and this book is a worthy companion to the first two ringworld novels