From Demon Camp: A Soldier’s Exorcism, by Jennifer Percy, to be published in January by Scribner. The book is an account of the two summers Percy spent reporting on a Christian camp for veterans with post-traumatic stress disorder.

April Somdahl’s trailer sits at the end of a wide dirt track near a patch of hundred-year-old North Carolina woods: a dark wall of yellow birch, flowering dogwood, witch hazel, wild strawberries, and the thick rise of spruce. Chickens nap in its shady border, burgundy heaps of damp feathers. A fence holds back the growth.

April didn’t want to move to…