Tales of a Monstrous Heart by Jennifer Delaney

Be careful of the dark and those that call it friend.

Katherine Woodrow is fey, and all she wants is to graduate from the Institute of Magic. But when the prejudiced mortal council threaten her position at the institute, she is left with only one option: accept a Mage Partnership with the elusive Lord Blackthorn.
Emrys Blackthorn is a riddle Kat is fearful of solving. The mysterious, cursed war hero with his stormy eyes and unpredictable ways leaves Kat with more questions than answers. What she does know is that she is irresistibly drawn to him . . . no matter how forbidden it might be.
When a string of murders and fey disappearances herald the return of dark magic, Kat and Emrys are thrown into a world of ancient books that hide hideous monsters, dark fiends who play with nightmares and mortal men who wish nothing more than to see them both burn.

But what haunts them both are secrets even ghosts dare not whisper, while insidious shadows lick their teeth and sharpen their claws, waiting for the moment that all tales will come to light – even the monstrous ones.