The Snow Queen's Shadow — Jim C. Hines

A broken mirror. A stolen child. A final mission to try to stop an enemy they never dreamed they would face.

When a spell gone wrong shatters Snow White's enchanted mirror, a demon escapes into the world. The demon's magic distorts the vision of all it touches, showing people only ugliness and hate. It is a power that turns even friends and lovers into mortal foes, one that will threaten humans and fairies alike.

And the first to fall under the demon's power is the princess, Snow White....