Exploring the Tropes: #1 - Unrealiable Narrators
The trope of the Unreliable Narrator has been used by the best: Edgar Allen Poe used it in The Telltale Heart, Vladimir Nabakov in Lolita did the same. Agatha Christie employed it in The Murder of Roger Ackroyd. In recent times the trope has served best sellers - Gillian Flynn's Gone Girl and Mark Haddon's The Curious Incident of the Dog in the Night-Time.
It's a means to tell a story in which the reader is either hoodwinked or remains suspicious as the narrative unfolds. However, the critical element in all of these novels is that credibility of the narrator - the reader needs to be invested in their experiences, even if there's a degree of doubt. They must appear real.
In the speculative genres this trope opens up all kinds of opportunities. Here are a few.
The Crazy
Anthony Burgess creates an ideal model for this category in A Clockwork Orange. The medical procedures and his existing mental state leaves us wondering what is real in Alex's narrative. In science fiction the narrator might be drugged into a crazy world or wakes up in one when their spaceship crash lands unexpectedly. Medical intervention to alter brain patterns is not unusual here. In fantasy the narrator might suffer from a magical spell that affects their perceptions of reality. There are two advantages here:
Perception is questionable - what is real? what it imagined? The reader can be introduced into one world and made to believe its reality to slowly question it as the other world manifests. It's best illustrated in the biography of the scientist John Nash in A Beautiful Mind where our perceptions are shaped by the main character.
Emotional reactions matter. Questionable perceptions can trigger empathy for anyone struggling to make sense of the world around them. Daphne du Maurier does it brilliantly in Rebecca. So does Yann Martel in The Life of Pi - how much of what happens in the boat is real? How much is shaped by the boy's trauma?
There's a darker side to this particular version of the trope. Iain Banks' The Wasp Factory leads you into a psychotic world where murderers appear in a different light. HP Lovecraft liked to set stories in asylums to mislead the audience. I've always wondered about writing a story where we follow the villain and engage with him/her emotionally, only to find out they're the one doing things wrong. How would that make readers react I wonder?
The Victim & The Manipulator
Gone Girl features here of course, a tale with the ultimate twist. This trope can also play around with the reader's emotions. As an apparent victim we're made to feel sympathy for the protagonist - but what if they're not the victim at all? I've read a bunch of fantasy stories where the manipulator turns out to be the baddie of the story, they've not just orchestrated events for the protagonist but for the reader too. This best illustrated by Zoe Heller's Notes on a Scandal where we learn about the teacher's affair with her pupil from the woman who is pulling the strings (played brilliantly by Judi Dench in the film).
In speculative fiction there are lots of ways for this happen - magic obviously. But Power is another way for people to be manipulated and made to appear to be the victim (when they are denied that power or suffer from its actions). Tales told from a victim's point of view can twist perception to show their misfortune - but what if it has been brought on themselves by their ruthless ambition? Think of those stories (in all SF shows in TV) where we meet people who appear isolated and badly treated - only to find out they are prisoners paying for the crimes?
The Desperate & The Liar
These two forms on Unreliable Narrators are driven to mislead us for motives which are not apparent at the outset - in fact they may not be disclosed until the end of the story. The People in the Trees by Hanya Yanagihara is a story of desperation and lies, where the prospect of eternal life is too tempting. American Psycho by Bret Easton Ellis is another story where it is the protagonist's genuine motives which remain hidden us. You find the same thing in Fight Club by Chuck Palahniuk. So what speculative-oriented motives might exist here?
A spy who infiltrates a country/planet/organisation to find their secrets
Escape from a place where danger lurks, like a zombie apocolypse
Adopting an alter-ego to rescue someone
Being on the wrong side of a war/revolution where staying hidden is vital
The Brain and its opportunities
Unreliable narrators might be psychic, which allows us to delve into telling a story from someone else's perspective, when the experiences belong to someone else. Or the brain is in another location - another body even (thinking Richard Morgan's Altered Carbon here). The concept of synthetic humanoids offers lots of options - is Decker in Blade Runner actually a replicant for instance?
Gene Wolf in his book Soldier of the Mist has his protagonist lose his memory. How many times has this been used? (Bourne Identity!) But it offers a variety of ways to tell a story in a disjointed way. You can really mess about with the storyline here, jumping around in time as memories return to gradually form a coherent narrative.
Also worth mentioning - how the brain deals with obsession. This can skew a character's view of Life - if they've taken drugs or they're always drunk - we can't tell what is real. This dependency or obsession can be motivated by external factors that help define the character in other ways - a soldier suffering from PTSD, a doctor unable to cope with stress, an adult with an awful childhood - these factors may provoke sympathy from the reader as well.
You can also tell someone else's story with this premise - a psychologist relating events from a patient. Or a programmer who has the files taken from the brain on a robot.
The brain provides a variety of options, not least because we don't understand it thoroughly. And what if, in a different race, the brain operates in unusual ways?
The unreliable narrator is a wonderful trope because despite the amount of time it's been around and all the times it's been used - there remains many more opportunities to squeeze a few more stories from it. I mean, why are there no stories about narcoleptics?