The first part of the film is well done. It is told from Nick’s perspective and the situation becomes more and more awkward. His wife is an extraordinarily popular writer. Her parents immediately set up a gigantic search team and involve the media to find their daughter. This results in a huge media circus. Fincher nicely shows how the media is manipulated to manipulate the public opinion.
About halfway the film becomes explanatory and the level drops. A few plot-turns and shifts of perspective make that the film is not boring, but it never again reaches the atmosphere of the first part. In sum “Gone Girl” is a descent drama/thriller, but not more than that.