A Murder of Crows — Jessica McBrayer

Amazon Top 100 Series.

After Sé and Thorn's nearly deadly encounter with Thorn's brother, Caleb, the couple heads to Ireland to recuperate at Thorn's ancestral home. As a witch, Thorn walks into a less-than-warm reception in the staunch Protestant town. And when children go missing, Thorn and Se are the first suspects. But those who remember Thorn and the old ways come to her for protection -- and to find the children.
While Thorn summons other witches for help, Sé's dreams are haunted by visions of his grandmother's death. Raven, Thorn's familiar, amasses a network of crows to spy and find the truth about the unfamiliar dark magick leaking out of the Mourne Mountains near Thorn's home. Soon Sé discovers new powers within himself while Thorn delves further into her wild magick. With the help of new friends and old, Sé and Thorn prepare to battle a force greater than any they've ever faced, one that will either destroy or transform them.