Hungry and crammed in a stuffy backseat on a long road trip through Mississippi, 13-year-old JoJo experiences the ghosts, both past and present, of America’s long and complicated history of race in Jesmyn Ward’s newest novel, “Sing, Unburied, Sing.” JoJo is on a road trip with his drug-addicted mother and her similarly addicted friend as well as his toddler sister to Parchman Farm, a Mississippi state penitentiary, to pick up his father, a white man whose family has a dark history with JoJo’s.