Elizabeth Marro’s affecting and beautiful first novel, “Casualties,” does not shy away from shame, regret and self-loathing — the underside of parenting. She takes us places we don’t want to go, makes us look, makes us feel. Her characters’ journey becomes ours and, as a consequence, we exult in their hard-won reckonings.“Casualties” begins on the West Coast, in San Diego, where Ruth Nolan, an executive for a company that supplies [...]