Unreliable narrator

An unreliable narrator is one whose account the reader has reason to doubt, because the narrator is mistaken, self-deceived, deliberately lying, or limited in a way the story quietly signals.

Wayne C. Booth coined the term in The Rhetoric of Fiction (1961): a narrator is unreliable when their values or their grasp of events differ from the implied author's.

Three broad types are worth telling apart. The limited narrator reports faithfully but does not understand — a child describing a marriage collapsing around them. The self-deceived narrator understands and cannot admit it, which is Stevens in The Remains of the Day. The deceiving narrator knows exactly what happened and is choosing what to tell you.

The craft requirement is the same in all three cases: the reader needs a route past the narrator. That route is built from discrepancy — what other characters do rather than say, the subject the narrator keeps returning to, the detail that does not add up, the insistence that is too strong for the claim.

Without those signals it is not unreliable narration, only a withheld fact. Readers can tell the difference, and the second one feels like a trick.