The setting of Niven’s 1984 novel The Integral Trees was striking and imaginative, even for this acclaimed world builder; it’s well worth the second visit made in this sequel. Around a neutron star an envelope of gas holds a breathable atmosphere and a strange profusion of plant and animal life, all floating in free-fall. Five hundred years after the crew of the Earth ship Discipline mutinied and deserted to this paradise, their descendants are still watched over by the ship’s unbalanced computer mind. The machine is busy manipulating its one small contact group into exploring the larger city they have been avoiding for years. Aspects of this society are intriguing: for instance, the disdain of the better-adapted taller, thinner people for the “dwarfish” throwbacks, even though only the short can fit into the scientific relics of the old ship. As usual with Niven, character and story are just an excuse for working out the properties of his wonderful imaginary world, where people can fly like birds and ponds full of fish hang in midair. Unfortunately, in this book he fails to marshal the visual and dramatic flair needed to show it off to best effect.