The unreliable narrator

I recently taught a course part of which focused on the unreliable narrator, a character who tells a story that the reader cannot take at face value. Now, I am working on a novel using a similar approach, which is proving great fun.
The technique has been used for many centuries but only became known as such in the 1960s.
Sometimes, the narrator is unreliable by the nature of the character, such terrible people that they cannot tell their stories objectively and resort instead to lies and deceit.
There is another type of unreliable narrator. This narrator is unreliable due to having incomplete or incorrect information, although initially neither the narrator nor the readers is aware of this.
Or the unreliable narrator may simply be deluded, suffering perhaps from an illness which clouds judgement (dementia is becoming a popular theme for many writers).
All are terrific techniques but there are dangers. For a start, readers do not always understand that a narrator is unreliable. To counter that, the unreliability of the narrator can be gradually revealed as part of the resolution. It is important to plant clues along the way to ensure that the reader understands and perceives the situation in a way that the narrator does not.
How can a writer do this? There are a number of ways, including showing the reactions of other characters, thereby telling the reader that all is not as it seems.
Although usually, the unreliability of the narrator is gradually revealed, some writers opt for a revelation at the end which shocks the reader.

 

John Dean