Winterly by Jeanine Croft

Emma Rose is just another London wallflower with no expectation of marriage. She’d far rather be a nun than an ornament on a man’s arm anyway. Except, her love of gothic books filled with ingenues romanced by evil counts in faraway abbeys is anything but vestal behavior.
When her beloved sister, Milli, is attacked by an unearthly creature, Emma finds herself in a contract of exchange for her life that defies all laws of heaven. Her world is torn apart and the reality she had known and believed in is revealed to be a facade, just like the masks of a midnight vampyre ball; a mask worn by Markus Winterly, the inimitable viscount and master of Winterthurse. Whether demon, vampyre, or monster, Emma discovers that these names are just facets to an ancient being who defies mortal comprehension. Spanning centuries, lifetimes, and the rise and fall of ancient civilizations, Winterly takes her on a journey of self discovery where Emma awakens to the truth of her identity at last, and she comes to learn that the line separating light and dark is as tenuous as her humanity.

When she surrenders to the call of her blood, she finds where she belonged all along. And it was never in London, an abbey, or even heaven, but in the arms of the devil himself.