The house of power - Patrick Carman

Three worlds are colliding....
Power is shifting......
Nothing will ever be the same again.....

Edgar, a gifted climber, is a lonely boy scaling the perilous cliffs that separate the three realms of Atherton: a humble fig grove, a mysterious highland world of untold beauty and sinister secrets, and a vast wasteland where he must confront an unspeakable danger that could destroy the people of Atherton.
When Edgar discovers a book which contains the history of Atherton's origins and ultimate apocalypse, his world - quite literally - begins to turn inside out.