King of Ash and Bone (Shattered Realms) (Volume 1)

When monsters break through the veil separating their worlds, Mackenzie Scott has nothing left to lose. Her brother is marked, her future has vanished, and all that remains is a desperate need for revenge. After discovering the breach the monsters used as a gateway, Mackenzie devises a plan to stop them, whatever the cost. It isn't exactly luck when she finds an injured stranger in the street, but he just might be the key she needs to succeed. What Mackenzie doesn't know, is that this stranger isn't the helpless boy he appears to be. He's one of them. And he's got plans of his own.