Here Be Monsters by Phaedra Weldon
Approx. 39,040 words.
Published on June 25, 2011 by
She is a Vampire. He is an Elf. His blood can give her the daylight again; but it can also restore power to an ancient race known as The Fallen, bent on destroying both Vampire and Elf. There is a forbidden curse that could destroy the Fallen, and save both races…
…but in order for it to work, the one who carries it must sacrifice their life.