What better place to fantasize about our troubling evolutionary path than Tomorrowland? Doctorow takes the scariest scientific advances -- -cloning, medical immortality, an inter-networked world in which social standing is based on eBay-style ratings -- -and sets them inside a Disney theme park. More specifically, those techno-possibilities are the backdrop for a battle over the Haunted Mansion. Members of the governing ''Ad-hocracy'' want to preserve the attraction's animatronic innards, but a techno-populist team from Disneyland Beijing has developed a way to flash-bake experiences directly into visitors' brains. The resulting tug-of-war leads to online insurrections, fan-led coups, and an assassination. The futuristic roller coaster that Down and Out travels is more fascinating than the murder mystery at its core. Still, Doctorow's debut is a sci-fi ride worth lining up for.