Atherton #1: The House of Power book by Patrick Carman

Edgar, a gifted climber, secretly scales the treacherous walls separating the three worlds of Atherton: the humble grove that is his home...a mysterious highland realm of untold beauty and sinister secrets ...and a vast wasteland below, where a monstrous danger lurks that could destroy them all. While searching the forbidden cliffs for a treasure lost in his faded memory, Edgar discovers the first of many startling revelations to come: the three realms are beginning to collapse, turning his entire world inside out. Atherton is not what it seems, but something far more dangerous, with a history locked inside the mind of a madman and a future beyond Edgar's wildest imagining. Published By Little, Brown Books for Young Readers on 2008-04-01