The Nightmare's Kiss by Skyla GRay

How can a living nightmare bring such sweet dreams?
Mara Vance never thought her "useless" psychology degree would lead to studying an actual monster. Subject X-13, aka "The Nightmare," is armed with sharp teeth, claws, and a constantly shifting form... yet Mara finds the huge shadow creature as intriguing as he is terrifying.
But as Mara studies him, she soon realizes that the Nightmare is far more intelligent than her shady superiors say he is. And every night, she indulges in twisted fantasies about the same monster. What happens in her dreams stays in her dreams - right?
Everyone says he's nothing more than a monster. But when dream and reality collide, Mara must decide how much she's willing to trust him - and herself. Will she risk setting him free, or will she lose him forever?