Rise of the Witch by Deanna Chase

Briggs Williams has a problem. For years he’d been unable to control his magic. But all that changed when he moved to Keating Hollow. There’s just something about the enchanted town that settles him. But when an old flame shows up in Keating Hollow out of the blue, his magic flares out of control again. Suddenly he’s a walking disaster. And there appears to be only one person that can help him keep his magic in check—Melissa Benson, the one woman he wants but knows he can never have.
Melissa Benson is determined to find her Mr. Right, instead of Mr. Right Now. If only she had a little bit of magic, she’d cast a love spell to help her find him. Unfortunately, she’s never been magical. It appears her only talent is dating emotionally unavailable men. Which is why she has sworn off the very handsome Briggs Williams, who has made it clear he’s not interested in anything permanent. But when his ex walks into town and Briggs asked Melissa to pretend to be his fiancée, she finds herself unable to refuse his insane request. Now she’s spending all her time with a man she can’t resist who is destined to break her heart.

Just when Melissa is determined to break off the charade, it becomes clear that she has magic after all, and if she leaves Briggs’s side now all hell will break loose. In order to keep Briggs and the residents of Keating Hollow safe, Melissa has no choice but to go through with the fake engagement at least until Briggs can regain control of his magic. But will she lose her heart in the process, or will she and Briggs find they can’t live without each other after all?