Hugo and Nebula Awardwinner Niven's latest (The Ringworld Throne, 1996, etc.) is set on planet Destiny, where the mothership Argo vanished into space, leaving the colonists with only two fusion-powered landers. Spiral Town was built along a rock-melt Road created by the heat of Columbiad's exhaust; the ship then settled permanently in Spiral Town, providing power. The other lander, Cavorite, extended the Road down the peninsula known as the Crab towards the distant mainland; it never returned. Now, hundreds of years later, all that links Spiral Town and its gradually failing technology with distant settlements are the trader caravans whose wagons, drawn by native chugs, bring goods and the essential dietary supplement, ``speckles.'' After young Jemmy Bloocher accidentally kills a caravan labor ``yutz,'' he flees along the Road; eventually, always curious about Cavorite's fate, he joins a different caravan as a chef. But when the caravan reaches the end of the peninsula, he finds that only traders are permitted to cross to the mainland--and aboard the return caravan are traders who would recognize him. After some amazing adventures, he reaches the mainland and settles alongside Cavorite in Destiny Town, which has retained advanced technology. As part of an experiment, Spiral Town has been deliberately isolated and kept dependent on the speckles brought by the traders. So Jemmy steals some fertile speckles--the seeds of a native plant--joins a caravan, and plants the speckles all along the Road back to Spiral Town. A fascinating and skillfully detailed alien ecology, along with solid characters and some intriguing problems for them to tackle: Niven in top form.