Monsters in the Mirror — A.J. Hartley

Darwen Arkwright's world is turned upside down when he is forced to move from a small English town to Atlanta in the United States of America. Feeling out of place and struggling to fit in at school, Darwen seeks solace in a mysterious shop full of mirrors. It's there that he discovers the ability to step through mirrors into different worlds - worlds beyond his wildest imagination. Darwen befriends creatures including Moth, a tiny being with mechanical wings, but he soon learns that there is a terrible darkness threatening this new world . . . and only he can save it. The problem with doors is that they open both ways. There are monsters inside, and some of them are trying to get out ...