Reign of Mist by D.G. Swank

Rowan might be the firstborn of the Whelan sisters, but her magic is far from first class. Outshone by her younger sisters’ rare and powerful gifts hasn’t been easy, but she has always taken her position as leader of their family seriously. Even more seriously when her sisters are endangered and they lose—yet again—the Book of Sindal, a magical tome of evil spells and incantations their small coven of three has been tasked to protect.

When the Dark Set, a group of mages determined to take over the magical community comes for Rowan, she turns to an unexpected and very human source. Local cop Logan Gillespie might not be a mage, but he’s not to be underestimated.

The question is why Rowan? As the weakest witch, she shouldn’t be of interest to the Dark Set. Yet they’re sure she’s the secret to unlocking the power of the book.

Can she convince them they’re wrong? She has to find a way because the lives of her sisters, Logan, and possibly the world depend on it.