Downsiders

History and urban folklore are wittily combined in Shusterman's (The Eyes of Kid Midas) well-wrought fantasy, centering on an alternative society that thrives undisturbed in the subterranean recesses of New York City. Despite stringently enforced rules against mixing with ""Topsiders,"" 14-year-old Talon sneaks aboveground into an Upper East Side townhouse. There he meets Lindsay, also 14, whose self-absorbed, divorced mom has left her with her equally inattentive dad ""for all eternity."" The friendless girl quickly forms a bond with the pale, otherworldly boy, and when he finds her again, she eagerly goes with him to tour his underground universe. However, Lindsay's presence, as well as some historical information she unearths, are as threatening to the Downsiders as the excavations for her father's West Side aqueduct project. Amidst the thrills and insider humor (Downsiders eat throgsneck soup and have hunted sewer alligators to extinction), Shusterman offers a crisply written coming-of-age story with a message worth pondering: ""Better that the truth be like the moon--a bright sphere only showing half of its face at a time, leaving the rest to be uncovered fragment by fragment, in its own proper time."" Ages 10-up. (June)