Creatures of the Night — C.A. King

When the black mist came, everything changed. An unusual anomaly in outer space opened portals. A black mist poured through, bringing something along with it. War fell upon the human race.Generations later the fighting continued... Zoe spent her whole life training how to fight monsters and demons—how to kill them. Not once did that curriculum include falling in love with one. Now, she's faced with a hard choice: betray one to save the other. Will she side with the family and friends who have always been at her side, or trade it all for the romance she so deeply desires? Odds are, no matter which path she follows, her heart won't make it out unscathed.