I just started reading it and so far, so-throroughly-enjoyable!
Here's the skinny:
WIZARD’S THIEF by CHRISTINE D’ABO
As Callie is sent into the Warren to steal the wizard’s binding stone, she enters a world she doesn’t understand. Stumbling into the arms of Raine, she learns that she is his connection to a powerful magic, and is bound to him for life. Raine, once the most powerful of the Warren’s wizards, has had his magic lost to him for years. He must learn to trust Callie, not only with the secrets of the Warren, but with his heart. Each passing moment brings the flare of passion between them higher as the control over his magic returns. When an old enemy threatens a member of the Warren, Raine must overcome his fears and trust Callie not only to save a friend, but to return the love he wants to give.
Buy it now at Ellora's Cave!