Look What You Made Me Do by John Lanchester

Kate, thirty years into her marriage, has a seemingly idyllic metropolitan, North London life. Phoebe, a young screenwriter, is the creator of the year's hit TV show, Cheating. When Kate's world takes a darker turn, she thinks she sees details and intimacies in the show that only she and her husband Jack could possibly have known. But who has betrayed who? Who gets to tell whose story?