Description from Google Books:

A witch and a hunter. Vengeance is their mission. Love is their destiny. Fritzi is a witch. A survivor of a brutal attack on her coven, she's determined to find her only surviving family member and bring the hexenjägers--zealot witch hunters--to justice for the lives they ended. To do this, she will need to take down their leader--Kommandant Dieter Kirch. Otto is a hexenjäger and a captain, the second in command to Dieter Kirch--but that's just his cover. Years ago, the hexenjägers burned his innocent mother alive and since then, he has been planning a move against the witch hunters that tore his family apart. And now the time has come for them to pay for what they've done. When Fritzi and Otto are unexpectedly thrown together, neither is sure they can trust the other, despite their common enemy. But all they have is one another, and they both crave revenge. As truths come to light and trust shifts, Fritzi and Otto uncover a far more horrifying plot at the center of the hexenjäger attacks . . . but their own growing feelings for each other may be the most powerful magic of all.

Snippet from Google Books:

Seeking to destroy the hexenjägers, zealot witch hunters, Fritzi and Otto are forced to trust each other due to their common enemy while being led to the heart of a Black Forest where they discover a horrifying plot--and their growing ...