Whoever has read the voluminous "Gone Girl", knows adapting such a book to film is by no means easy. But I dare say the screenplay, adapted by the author herself and directed by the seasoned Fincher, is a well-thought and well-implemented summarization, showcasing the novel's main message even better than the book itself; which is: How well do you know your spouse? The implications of that question are grounds for a horror movie, which including a masterfully-directed hard-to-forget murder scene at the end, is exactly what this film becomes. The end-result will make you self-aware about the concept called marriage.
PS; Reading the book, I had Paddy Considine and Reese Witherspoon in mind as people who could play the roles of Nick and Amy. But Affleck and Pike work just fine too. And Witherspoon is actually one of the producers. Some empathy, perhaps?