A Study in Drowning by Ava Reid

blurb:

Effy Sayre has always believed in fairy tales. Haunted by visions of the Fairy King since childhood, she’s had no choice. Her tattered copy of Angharad—Emrys Myrddin’s epic about a mortal girl who falls in love with the Fairy King, then destroys him—is the only thing keeping her afloat. So when Myrddin’s family announces a contest to redesign the late author’s estate, Effy feels certain it’s her destiny.

But musty, decrepit Hiraeth Manor is an impossible task, and its residents are far from welcoming. Including Preston Héloury, a stodgy young literature scholar determined to expose Myrddin as a fraud. As the two rivals piece together clues about Myrddin’s legacy, dark forces, both mortal and magical, conspire against them—and the truth may bring them both to ruin.