The Shadow Keepers — Marisa Noelle

Sixteen-year-old Georgia Boone has seen the shadow creatures in mirrors and other reflective surfaces since she was six-years-old. But no one--not even her
brother, the person she's closest to in the entire world--believes her. She is all alone in the hellish world where crow-like creatures hunt her everywhere she goes

When an afternoon of shopping ends in violence and blood, Georgia is sent to the UK's most prestigious mental health hospital: Brookwood Hospital.
There, she's forced to face her fears and answer the question:

Are the shadows real, or is this all in her head?

At Brookwood, the shadow creatures are more present than ever. Each day they grow stronger. With the help of a mysterious boy who lives inside the mirror world, she might be able to prove that she's not hallucinating and stop the shadows from destroying the human world.