In Edgar Allan Poe's short story "The Cask of Amontillado" the narrative is told from a first person point of view. The first person narrative is that in which the pronoun "I", or "We" is used because the person speaking is directly linked to, or has been directly affected, by the story.
In this case, the character of Montresor tells his story about how his relationship with Fortunato has deteriorated to the point of death.
The problem with the first person narrator is that we, as readers, have to "take his or her word for it" when it comes to the narrator's telling of events.
He had a weak point --this Fortunato --although in other regards he was a man to be respected and even feared. [...]In painting and gemmary, Fortunato, like his countrymen, was a quack, but in the matter of old wines he was sincere. In this respect I did not differ from him materially; --I was skillful in the Italian vintages myself, and bought largely whenever I could.
We get the feelings and thoughts of other characters according to what that first person speaker says. There is no other way to know whether we are being told things exactly as they happened. This is what makes the first person narrative also subjective and limited.
Therefore, while the first person narrator is easier to read and relate to, this type of narrative is also flawed in that it is not objective, nor does it have to be true. Unfortunately, what Montresor says of Fortunato is pretty negative, and we will never really know what prompted the actual dislike as Montresor would never truly open up and say whether he was jealous, envious, or even obsessed with his former friend. All that we have is what he is willing to offer us, which is merely what he feels and thinks within his crazy mind.