Suspense, secrets, and unsolved crimes all make Gone Girl fit the classic definition of a mystery novel. Still, Gillian Flynn gives the story a modern twist that pushes it outside the genre's box.
At the beginning of the story, Gone Girl looks like a tale we've all seen multiple times in books, movies, television, and even in the news: a beautiful, likeable woman disappears and her husband is the primary suspect. After Part One, though, the story takes a shocking turn when we learn Amy is the real criminal—she's still alive and framing Nick for her murder as payback for his affair with Andie.
From then on, the focus of this mystery changes from who dunnit to whether or not Amy will get away with it. "I've always thought I could commit the perfect murder," she says once we learn that she's alive and well and living in the Ozarks. "People who get caught get caught because they don't have patience, they refuse to plan" (32.14). We may be debating Nick's guilt right along with Rhonda Boney and Ellen Abbott's audience at the beginning, but around the middle, we find out the real villain's identity, and a whole new mystery unfolds.