Marked by the Moon (Nightcreature #9)

Tough as nails Alexandra Trevalyn does what most people can't: She kills werewolves. Once part of an elite group of hunters, she's going rogue these days, though no less determined to rid the world of bloodthirsty beasts -- once and for all. That's why Alex had no choice but to kill Julian Barlow's wife -- and will have to pay the price. Julian's brand of vengeance is downright devious, and now he's turned Alex into a member of his pack. It's only a matter of time before she falls under his spell. With the wild freedom of the wolf in her veins, Alex can't deny that Julian wakes her most primal passions -- and draws her that much closer to the moon's call, where evil lies in wait.