Pestilence (The Four Horsemen, 1) by Laura Thalassa

They came to earth―Pestilence, War, Famine, Death―four horsemen riding their screaming steeds, racing to the corners of the world. Four horsemen with the power to destroy all of humanity.

They came to earth, and they came to end us all.

When Pestilence, the first of the horsemen, comes for Sara Burn's town, one thing is certain: everyone she knows and loves is marked for death. Unless, of course, the angelic-looking horseman is stopped, which is exactly what Sara has in mind when she shoots the unholy beast off his steed.

Too bad no one told her Pestilence can't be killed.

Alive and furious, the horseman takes Sara prisoner, determined to make her suffer for impeding his mission. Despite her pleas, nothing and no one gets in the way of his orders to destroy humankind. Only, the longer Pestilence spends beside Sara's bravery and compassion, the more he seems to understand her, and understand humanity. And the longer Sara travels with Pestilence and his plague, the more uncertain she grows about his true feelings toward her…and hers toward him.

Sara might still be able to save the world, but she'll have to sacrifice her heart in the process.