It's a very difficult era in which to be a person, just a real, actual person, instead of a collection of personality traits selected from an endless Automat of characters.
Wife goes missing, all the evidence points to the husband. Initiate the predictable flow of personalities, motives, and plot lines you'd expect. The husband-narrator who won't admit to the reader that he didn't do it; the perfect wife, writing in her diary, about their almost-perfect relationship with hints of doom and gloom on the horizon. The mistress, the detectives, the parents of the missing wife, the media, etc. etc. etc. etc.
We've all heard this story a million times.
Except not. Flynn has done something remarkable; she has taken an over-told story and turned it into a page-turner thriller that presents compelling questions about: 1) personal identity in a society over-saturated with personalities/narratives, 2) the role of mass media in criminal investigations, 3) relationships, and 4) narratives and counter-narratives. (to name a few).
Flynn also does an excellent job of causing the reader to root for the wrong ending, multiple times. Given that there is a major twist after the first part, it's remarkable that she nonetheless can trick the reader again later.
To shift focus to the thing of most interest to this reader, Flynn gives us a lot to think about re: media intervention in criminal cases. Our constitution enshrines two rights that butt heads: our right to a fair and impartial trial and our right to a free press. These rights crash into each other when we have a trial by media(fire): the media tells the narrative that sells, this is not always the narrative compelled by the (admissible) evidence. Why should we care? Because, when the media is telling everyone that a defendant is guilty, trifling things, like reading someone his Miranda rights, seem like an unnecessary interference in the guilty-verdict-machine.
Gone Girl, then, serves as a reminder that trial by media is an extremely broken process. The media loves guilt-narratives, and hates defendants' rights narratives. The presentation of the guilt narratives is destructive of how we feel about the criminal justice system. I distinctly remember my aunt's response after Casey Anthony verdict: "I just don't understand how, with all that evidence, that jury could have found her not guilty." However, she had not watched any of the trial at all. (I also have not, but I do not purport to have an opinion as to her guilt). I digress only to note that Gone Girl does not shy away from these questions, but embraces them and uses them to move the plot.
And that is only one thread, of many, that Flynn effectively gets across. Definitely worth a read.
Hat tip to Brittany's and Billy's respective reviews.