This one is more prevalent in the film rather than the book. Is Amy just pure evil or a Jerkass Woobie? Given she was willing to kill herself as the major part of her plan and wants to come home after Nick shows he's capable of being the husband she remembers, it seems possible to view her actions as not simple psychosis but being desperately unhappy. Rosamund Pike's performance also seems to indicate that Amy genuinely loved Nick in her own way but felt betrayed by his attempt to box her in as his unwanted nagging wife from New York. This is despite the fact she moved across the country to a small town in order to be with him, and he barely made an effort to repair their marriage when it started to strain.
Oddly, averted with Nick. Is Nick the grieving husband, a Nice Guy, and cool sophisticate who is the first person to ever treat Amy as a person? Or is Nick a borderline misogynist, a controlling asshole, and unambitious loser who gave up on a prestigious life in New York to become a community college professor who sleeps with much-younger students? The answer is, he's all of these things. Nick is a multifaceted guy with both dark and light qualities; qualities which come to the fore depending on his circumstances or desire to show them.
In spite of everything, does part of Nick still love Amy in spite of being terrified of her? After all, she did literally kill for him. Go accuses him of wanting to still be with her and might have a point.
His last line to Amy, that he feels sorry for her, has two possible meanings. Does he genuinely pity her out of the goodness of his heart? Or is Flynn showing us that Nick is playing the game on Amy's level, and knew that saying that was the best way to get under her skin?
Did Greta ever figure out who Amy really was, or was Amy just paranoid? This one's even debated by Amy In-Universe.
For that matter, did Greta rob Amy out of pure greed, or was she angry and spiteful over Amy, who has never been abused the same way Greta was, exploiting the sympathy people have for women who were actually abused? Her line in the movie, "I can tell you've never been hit in your life!" followed by her punching Amy adds credence to this idea.
Did Andie reveal her affair with Nick to the public solely to get back at him for dumping her? Or did she truly believe he might be guilty? Or did she figure that the affair would get out anyway, and decided to beat Nick to the punch so she could be in control of the narrative, thus being more able to cover her ass?
The "Cool Girl" speech has divided feminists over whether Amy is making a good point about women changing themselves into The Lad-ette to attract men or whether she's just condemning women who don't fit her ideal of what is proper behavior. The movie subtly argues that Amy is wrong by singling out women, failing to see that humans in general behave that way - this is highlighted by her wrongly identifying one of the women in a car she passes by as a "Cool Girl", someone who plays up to men's fantasies, only for the camera to reveal the other passenger is actually another woman. And that's not even getting into Amy's evil, violent actions. There's also a third camp that thinks that Amy brings up some good points and isn't entirely wrong, but you also probably shouldn't take everything she says at face value.
The work as a whole tends to inspire passionate feelings for or against, with fans seeing it as a twisted, jewel-like labyrinth of a psychological thriller, with a fascinating antagonist and keen criticism of modern day gender roles. Detractors tend to think that Flynn plays into the very same reductive, sophomoric gender roles she pretends to tear down, and claim that the narrative is riddled with plot holes and nonsensical character decisions, even after The Reveal.
Critical Research Failure: A mild but still annoying example in the book. When Nick enters the wrong code for his dad's house and trips the alarm, he calls the monitoring station. They turn it off for him, which can't be done remotely.
Darkness-Induced Audience Apathy: It is possible to have this kind of reaction to either the book or film. While the characters are capable of Pet the Dog moments or moments of genuine empathy, most of them can be distrustful, shallow, unfaithful, self-centered or at the very worst, sociopathic. Throw in an ending that's pretty bleak, especially in the film version considering the softer version of Nick's character, and you got something of a bitter pill to swallow.
Nick gets this as well, though far, far less often than Amy does. While he was by no means an innocent man, hes still not entirely the victim he ended up being viewed as by those who treat him as such, representing his own crappy end of what both characters separately represent, with both being horribly suited for one another.
Amy does terrible things to people who were repentant about their mistakes, but it's implied that being brought up to be 'Amazing Amy' left some considerable emotional damage on her ("I remember always being baffled by other children. I would be at a birthday party and watch the other kids giggling and making faces, and I would try to do that too, but I wouldn't understand why.") Her parents expected her to be perfect, and each day was an opportunity to fail.
Nick is a deeply flawed man, but he so did not deserve the shitstorm he went through at Amy's hands. And, as of the ending, he's stuck in his awful situation until either he or Amy drops dead.
"I'm the cunt you married. The only time you liked yourself was when you were trying to be someone this cunt might like. I'm not a quitter, I'm that cunt. I killed for you; who else can say that? You think you'd be happy with a nice Midwestern girl? No way, baby! I'm it." Variations of this speech are starting to pop up on Tumblr and other sites.
"What are you thinking? How are you feeling? Who are you? What have we done to each other? What will we do?" is everywhere on Tumblr.
Some fans legitimately believe that Amy is a feminist role model despite (or because of?) her being a complete and utter manipulative sociopath, up to applauding her murder of Desi and her framing of Nick. She's also been held up by some men (and women) as their dream girl.
Likewise, some fans of the book (movie Nick is far more sympathetic) believe Nick is a flawed but ultimately sympathetic everyman utterly wronged by his wife, when the two of them are a pair of sociopathic individuals trapped in a mutually abusive relationship.
Ron the Death Eater: Movie Nick is a deeply flawed and unlikable man, no doubt, but he's hardly as bad as Amy, who murders a guy and frames Nick for her own just because he was cheating on her. While an icy and unfaithful husband with potentially sociopathic traits, he's hardly the embodiment of pure evil fans like to paint him so everything Amy has done can be excused.
The Woobie: Go is probably the biggest contender- she has to helplessly watch as her twin brother is accused of murdering his own wife, discovering that he has lied to her and has the press constantly asking if she was involved in Amy's disappearance. By the end of the story she also has to live with the knowledge that her brother intends to stay with a manipulative, murderous psychopath.
Esoteric Happy Ending: The ending is deliberately written to be this. Amy finally has someone who she can be herself with and Nick has the child he always wanted. They may eventually kill each other but, at heart, they're both sociopaths.
Genius Bonus: When Nick is recounting Amy's obsession with finishing everything, he remembers her reading Haruki Murakami's "The Wind Up Bird Chronicle", which is about an estranged couple, along with the wife suddenly going missing.
Amy makes a reference to The Aeneid when she calls their town New Carthage (Its real name is North Carthage; Carthage is the site of Aeneas' romance with Dido, which was, to say the least, destructive). Nick is annoyed that he doesn't get the reference.
Shocking Swerve: A book-exclusive one: Amy shows up bloodied on Nick's doorstep after murdering Desi. The movie averts this by showing the earlier of the two events in question before showing the one that takes place chronologically later.
Nick comes across as less of a sociopath in the film; he's prone to emotion, genuinely cares about people, and empathizes. To be sure, he's a schlubby kind of guy and painfully awkward when out of his comfort zone (read: the entire movie), but his faults are presented as more of the garden-variety mid-life crisis type. This more human characterization has the side effect of making the already dark ending bleaker in the film than in the book. Book Nick seems excited by Amy and willing and able to manipulate her in turn; film Nick comes across as disgusted but powerless and any fascination with Amy is more akin to Stockholm Syndrome than anything else.
In a blink and you'll miss it moment, Nick's throwaway line of them being "partners in crime" seems to imply he's not quite the trapped victim Amy hoped for, especially after their earlier confrontation. Amy looks visibly surprised by the comment.
Another minor example is the film not revealing that Nick's father emotionally abused his mother and family. This makes Nick's interactions with him much more open to interpretation and potentially makes him much more unsympathetic.
Andie comes off as more shallow and vapid than her book counterpart thanks to a comparative lack of screentime—was she sleeping with Nick because she genuinely loved him, or did she just think that it might give her a leg up in her career?
You can be much happier in marriage if you both pretend to be better people than you are.
Don't cheat on your spouse, ever.
Never get married.
Don't get married to a sociopath.
If you're unhappy in your marriage, just get a fucking divorce.
Author's Saving Throw: The movie shows a scene that was only discussed in the book, but was criticized for not including the event in the narrative: Amy's murder of Desi, in all of its gory details.
Award Snub: Was only nominated for Best Actress at the Oscars. No nominations for Gillian Flynn for Adapted Screenplay, David Fincher for Director, or Trent Reznor/Atticus Ross for Original Score, or Best Picture.
Awesome Music: As always, Trent Reznor and Atticus Ross' score is a highlight. Especially the tracks that plays over Nick discovering the contents of the woodshed, the "Cool Girl" speech, Amy's murder of Desi, and the amazingly eerie opening title track.
Few would question Neil Patrick Harris's skills with comedy, but here he plays a completely dramatic, and rather creepy, character, and pulls it off without a hitch.
Harsher in Hindsight: Ben Affleck was involved in cheating allegations a few months after the release of the movie, and his wife filed for divorce shortly after. Some paparazzi photos of him with his kids were pointed out to look extremely similar to Nick's expression at the initial press conference.