Hourglass. Claudia Gray. 2010.

Bianca will risk everything to be with Lucas.

After escaping from Evernight, the vampire boarding school where they met, Bianca and Lucas seek refuge with Black Cross, an elite group of vampire hunters. Bianca must hide her supernatural heritage or risk certain death at its hands. But when Black Cross captures her friend—the vampire Balthazar—all her secrets threaten to come out.

Soon, Bianca and Lucas are on the run, pursued not only by Black Cross, but by the powerful vampires of Evernight. Yet no matter how far they run, Bianca can't escape her destiny. Bianca and Lucas have always believed their love could survive anything—but can it survive what's to come?