Adaptational Displacement: Most people don't know at first that this film is actually an adaptation of a book called Tony and Susan. Notably, after the films release, the book was re-released and the title was changed to Nocturnal Animals as well.
Is Rayreally supposed to be a second Expy for Susan? The only real indication of this is when he taunts Tony by repeatedly calling him "weak", which is what Edward accuses Susan of thinking he is in the flashbacks. The character saying this could just as easily be Edward confronting the idea in general that he is weak, as we had just before seen a sequence where Tony breaks down over his failure to protect his family.
Is Edward supposed to be viewed as sympathetic, let alone justified, in his "present-day" behavior? The implication is that the entire reason he wrote the novel is to take emotional revenge on Susan for leaving him, and for possibly aborting their child. Solidified by the fact that from the beginning, he sets up a reunion with Susan...only to not show up in the end. Is he really The Woobie, or a spiteful, petty Jerkass who refuses to even see if she's changed?
On Edward standing Susan up - was it pure spite, was he afraid of seeing her or was it a point about how Susan ran away from her problems in their marriage to Hutton, and now wants to run away from Hutton to Edward and assuming Edward would drop everything to get back together with her?
Award Snub: Even though he took home the Golden Globe Aaron Taylor-Johnson wasn't nominated for Best Supporting Actor at the Oscars, though Michael Shannon was nominated in his place. The film also wasn't nominated for Best Picture, Director, Cinematography or Adapted Screenplay. Also, despite pre-release hype, Amy Adams wasn't nominated in any award selection for Best Actress for her role, nor was Jake Gyllenhaal nominated for Best Actor.
Awesome Music: Abel Korzeniowski's score, which managed to set the mood and be memorable all the same.
Complete Monster: In the titular in-universe novel, Ray Marcus is a sadistic thug hiding behind a veneer of smug innocence. Running the Hastings family off the road on an abandoned highway, Ray terrorizes the family alongside his gang before kidnapping, violently raping, then murdering Laura and her teenage daughter India. Attempting to kill the father, Tony, in the process, Ray goes on to continue his crime spree before feigning ignorance when confronted by Detective Andes on his past rape charges and attack on the Hastings. Upon finally dropping all pretense of innocence, Ray cheerfully brags to Tony that he raped and killed the man's family out of mere pride and because "killing is fun", before trying to bludgeon Tony with a fireplace poker.
Ensemble Dark Horse: Detective Bobby Andes was probably the most well-received character in the film, due to being an effective and hardcore yet still believable portrayal of a Cowboy Cop. Michael Shannon's performance got him an Oscar nomination for Best Supporting Actor.
He Really Can Act: Aaron Taylor-Johnson is cast well against type here, and those who only know him for his acting in blockbuster movies were surprised by how nasty and unpleasant he was. Not surprisingly he was nominated for, and more surprisingly won a Golden Globe for his chilling performance.
Iron Woobie: Detective Andes. He's not the type to break down in tears at all, but his character is still remarkably pitiable.
Susan's obvious expy in the book, Laura, is played by Isla Fisher, whose uncanny resemblance to Amy Adams has become a popular Internet meme. This film just served to revive the meme all over again.
For some time, people recorded themselves or their friends who knew nothing about the movie reacting to the surreal, Fan Disservice-laden opening scene.
Narm: Susan is obviously hurt and disappointed that Hutton didn't show up for her new art gallery. Though it is clearly meant to highlight the very serious estrangement between wife and husband, but it's funny since we know the art gallery he didn't show up for featured an array of nude, old, obese women doing erotic dances and poses; most viewers found this incredibly bizarre even in-context. Amusingly, the distant husband is somewhat Unintentionally Sympathetic in this case.
The Hastings' first time meeting Ray Marcus is insanely tense, beginning with Ray taunting the family and going out of his way to humiliate Tony in front of his family and concluding with Laura and India being forced into a car and driven off so Ray and his gang can have their way with them.
Tony finding his wife and daughter dead and stripped naked out in the desert. Worse part is when Detective Andes describes what was done to them before their murders, made even worse when he reveals that the one who suffered the most was India.
One-Scene Wonder: Laura Linney has only one scene as Susan's mother, but she makes it memorable. The same could be said of the characters played by Michael Sheen, Andrea Riseborough, and Jena Malone.
Paranoia Fuel: If you and your family are planning on taking a long drive down some desolate, open-country roads, this is definitely not the movie you want on your mind.
Too Bleak, Stopped Caring: Between the relentlessly bleak story that Susan reads, her present day life which involves being friends with insufferable bourgeois-types and a possibly cheating husband, and her rather rough past-relationship with Edward in flashbacks, the film doesn't shy away from showing how bad relationships or even people can be. Combine it with a Downer Ending for each story and you've got a story that isn't exactly one would call a Sunday afternoon viewing.
The Woobie: Susan Morrow, the story's protagonist, and Tony Hastings, the protagonist of the in-universe novel. Edward Sheffield, Susan's ex-husband and the novel's author also counts, but in the end it can be argued he's become more of a Jerkass Woobie.
playing over Susan's attempt at reuniting with Edward only to be left alone. Roll credits.