Knights of the borrowed dark

"The first book in a new series about an orphan boy who discovers he is part of a secret army that protects the world from a race of shadowy monsters. Grey placed his finger in the middle of the shadow. Whats this? he asked. Denizen frowned. Its a shadow. No it isnt Grey said. Its a door. Denizen Hardwick doesnt believe in magic - until hes ambushed by a monster created from shadows and sees it destroyed by a word made of sunlight. That kind of thing can really change your perspective. Now Denizen is about to discover that theres a world beyond the one he knows. A world of living darkness where an unseen enemy awaits. Fortunately for humanity between us and the shadows stand the Knights of the Borrowed Dark. Unfortunately for Denizen hes one of them . . ."