Total Eclipse of the Moon by Zoe Forward

If he doesn’t break the curse tying him and his brothers to the Crown of England as paranormal terrorist hunters, they’ll be forced to execute him.

An accidental demon possession erodes Shane Lanzo’s sanity. Sometimes he’s in control. Sometimes not. His only hope is the witch who cast the curse, which is a problem. The last two times he approached her, the feisty enchantress somehow tamed the demon inside him, but rendered him useless against his desire for her.
Madeline Edney sucks at being a witch. Her casting the curse on the lycan brothers was a fluke, and it destroyed her life. She’s been hunted by the Crown ever since to make sure she doesn’t try to undo the curse. She never expected Shane to find her so easily. He’s a temptation that promises zinger chemistry, her absolute weakness. One taste was gratifying. Two was foolish. Three has become an addiction. Lifting the curse requires she forfeit her life, but if the hunters kill her, it leaves Shane at the mercy of the Crown. Either way she dies.

Shane has a choice: freedom for his family, risking Madeline in the process or a chance at happiness with the witch who fated his brothers as prisoners for eternity.