The narrator is not the author. The narrator is a voice the author built for the occasion, and the difference is where most misreadings start.

A first-person narrator knows only what the character knows, which means you can be misled alongside them — sometimes deliberately. A narrator who reports from outside sees actions but not thoughts. An omniscient narrator knows everything, including what the characters conceal from each other.

Changing the narrator changes the story even when every event stays the same. A crime told by the guilty party, by a bystander, or by a voice that knows all of it is three different texts. So the first question to ask of any narrative is not "what happens?" but "who is telling me, and what can they not see?"