This Savage Song

Kate Harker wants to be as ruthless as her father. After five years and six boarding schools, she's finally going home to prove that she can be.
August Flynn wants to be human. But he isn't. He's a monster, one that can steal souls with a song. He's one of the three most powerful monsters in a city overrun with them. His own father's secret weapon.
Their city is divided.
Their city is crumbling.
Kate and August are the only two who see both sides, the only two who could do something.
But how do you decide to be a hero or a villain when it's hard to tell which is which?
Corsai, Corsai, tooth and claw,
Shadow and bone will eat you raw.
Malchai, Malchai, sharp and sly,
Smile and bite and drink you dry.
Sunai, Sunai, eyes like coal,
Sing you a song and steal your soul.
Monsters, monsters, big and small,
They're gonna come and eat you all.