Alternate histories can be a treacherous siren call within genre fiction. While a tantalizing “What if?” is enough to get readers in the door, without a crackling story, hypothetical worlds devolve into strings of bizarro, clever-clever factoids. And yet Winters’ nightmarish mystery, set in a modern-day U.S. where the Civil War never happened, somehow manages to tap-dance around every potential pothole. In the foreground is Victor, a black off-the-books slave hunter, and his search for a missing PBL (Person Bound to Labor). Winters crafts his thriller so deftly that the ingenious details of his sideways timeline often fly under the radar, blurring the line between Victor’s world and ours. A–