Martyr : The Hunted, book one

Three years have passed since magic destroyed the world.
Those who remain struggle to survive the monsters roaming the streets, fighting back with steel and magic—the very weapons that birthed the Howls in the first place.
Tenn is one such Hunter, a boy with the ability to harness the elements through ancient runes. For years, the Hunters have used this magic to keep the monsters at bay, but it's never been enough to truly win the war. Humans are losing.
When Tenn falls prey to an incubus named Tomás and his terrifying Kin, Tenn learns there's more to this than a fight for survival. He's a pawn in a bigger game, one with devastating consequences. If he doesn't play his part, it could cost him his life, his lover and his world.