Brand New Moon (Crescent Deveyne Chronicles Book 1)

Crescent Deveyne is a witch. At least, she would be if she had any powers.
Everyone else in her family is magically blessed. All Crescent wants is to fight alongside them in the war against evil. But, as her eighteenth birthday comes and goes, she begins to believe her destiny is a lie.
Then, before the day is over, Crescent finds herself leaping into action to save a girl from a brood of vampires and inadvertantly discovers that her powers may not be lost at all.
So begins Crescent's quest to reclaim what is rightfully hers. But, with lives at stake and the fate of the world hanging in the balance, the price to becoming a witch may not be one she can afford to pay...