Cruel Is the Light by Sophie Clark

An epic new fantasy about a demon hunter and a foot soldier thrown together in a centuries-old war. . . and the forbidden love that could change the course of history.

A bloody war between demons and the Vatican has waged for more than a century, with two elite soldiers now at its center: Selene Alleva, a high-ranking exorcist running from a dark family legacy, and orphan Jules Lacroix, recruited by the Vatican and unrivalled on the battlefield.
When their paths cross over a series of unprecedented demon attacks, the distrust–and unwelcome attraction–they have for each other is immediate. But to get to the bottom of the breaches they strike an uneasy alliance to avoid suspicion. With Jules posing as Selene’s estranged fiance, they head to the Vatican in search of answers. But even as Selene questions who her most dangerous enemy is, Jules has begun to suspect that it’s him.
Now Jules’ very existence challenges every truth Selene thought she knew, and suggests a terrible conspiracy at the heart of the Vatican. Unable to ignore their growing feelings, the two must make an impossible choice between love and duty.

They say love conquers all – but can it win in a war between demons and exorcists? Or will it tear them apart . . .