This is a sequel to Hunters of the Red Moon, which should be read first. In that book, Dane, Rianna and Aratak are the kidnapped "prey" in a hunt involving species from different worlds. Think "The Most Dangerous Game" or Gladiator. That one was a fun, entertaining and fast pulp read. In this one the trio moving on to new challenges is investigating a "Closed World" full of unknown dangers. No one would claim this as great literature, and it's not the kind of thing you can enjoy if you nitpick the science and social assumptions to death. This is pulp fiction, with characterizations of the kind of depth you find in costumed superheroes in comic books. That doesn't mean this isn't enjoyable, although I enjoyed the first book more. But I don't think this matches in quality the best of MZB's Darkover books. (Otoh, it's better than the weakest in that series.)