Alpha and Omega, book 1 of 6, ongoing series

Anna never knew werewolves existed, until the night she survived a violent attack and became one herself. After three years at the bottom of the pack, she'd learned to keep her head down and never, ever trust dominant males. Then Charles Cornick, the enforcer and son of the leader of the North American werewolves, came into her life. 

Charles insists that not only is Anna his mate, but she is also a rare and valued Omega wolf. And it is Anna's inner strength and calming presence that will prove invaluable as she and Charles go on the hunt in search of a rogue werewolf, a creature bound in magic so dark that it could threaten all of the pack.