An engrossing horror/fantasy hybrid, this page-turner will be best appreciated by those with a taste for ambiguous endings. Sixteen-year-old Jack narrowly escapes a kidnapping by a menacing figure who drugs and nearly rapes him. Soon after, he and his best friend, Connor, embark on a planned trip to England, where a strange man gives Jack a set of purple eyeglasses that transport him to an alternate universe called Marbury whenever he wears them. In this post-apocalyptic world of ghosts and monsters, Jack and others struggle against the attacks of roving bands of creatures, once human, who have transformed into grotesque cannibals, and Jack’s grip on reality becomes increasingly tenuous. Nightmarish imagery is chillingly effective, and the pacing superbly builds suspense. Connor’s unrelenting teasing of Jack (including the oft-repeated suggestion that Jack’s virginity means he must be gay) is authentic in its portrayal of the experience of close friendship between some teen boys. However, in the end there are many questions left unanswered—which may well prove frustrating to readers expecting an explanation of Jack’s experiences. (Horror/fantasy. 16 & up)