Edna St. Vincent Millay

Where you used to be, there is a hole in the
world, which I find myself constantly walking
around in the daytime, and falling in at night.

The Kept by James Scott

The Kept is not a typical novel yet it kept me transfixed. Elspeth is a midwife who has stolen her children and they, in turn, were taken from her in a horrific act of violence. Her husband, Jorah, stays by her because he promised to stand by her no matter what even though he is troubled by what his wife does. 

Caleb moves to the barn after his father commits an inconceivable act. He alienates himself from his family and becomes more animal-like. When three strangers murder his family, though, he and his mother form a pact. The commit themselves to finding these men and seeking revenge. Much like a Western, the heroes of The Kept try to live honorable lives in a fallen world. 

Other books with similar themes: The Thicket by Joe Landsdale.
Non-fiction books with similar themes The Searchers: The Making of an American Legend by Glenn Frankel and Captured by Scott Zesch.