Hugo Award-winning novelist Simmons's ( Hyperion ) has produced an outstandingly eerie and truly horrifying tale, a page-turner of the first order. A miasma of evil hangs over the bright summer streets of the small town of Elm Haven, Ill., perceptible only to a group of boys who have just finished their last year at Old Central, an oversize, grotesquely ornate grade school built in the previous century. When one of the students disappears on the last day of school, some of the youngsters decide to investigate. A man dressed in World War I uniform begins to follow them, as does the rendering truck, driven by the school custodian Van Syke, a vehicle that stinks from the animal carcasses it carries. When one of the boys uncovers ties among Old Central, children who vanished at the turn of the century and an ancient evil from the Old World, he is killed in a vicious fashion by creatures of the night. The other boys move to defend themselves, knowing they will not be believed by the adults, especially because the horrors appear to be directed by the respected principal of the school. Simmons impeccably evokes a small Midwestern town in 1960, peopling it with appealing--and appaling--characters. His slow and careful introduction of the elements of evil builds credibility and moves to a high-pitched intensity. BOMC alternate. (Feb.)