Chase the Moon by Sharon Sala

Elijah Moon, his sons, his beautiful daughter Gracie and their families are trying to dwell simply in this modern world. Living off the land in rural Kentucky, they adhere closely to the words of the Bible. But there is more going on at their compound than either Elijah or Gracie realises. In fact, a man has been killed for knowing too much. When the victim's twin, Jake Baretta, arrives at the compound to search for his twin's killer, he struggles to keep his heart and attraction to Gracie to himself, and his mind on the job. Everyone knows the first rule of undercover work: Never fall in love with enemy.