Fight Club’s unnamed narrator is widely considered unreliable because of his fragmented psyche, which has been read by some critics as a representation of Dissociative Identity Disorder (DID).
The novel’s famous “twist” is that the Narrator and his companion Tyler Durden are actually the same person—Tyler represents the Narrator’s unconscious desires. As a result, the Narrator often can’t remember his own actions, instead assigning responsibility to “Tyler” for things he, himself, has done:
The bar is empty, and the bartender says, "Welcome back, sir.”
I’ve never been to this bar, ever, ever before.
I ask if he knows the name Tyler Durden.
The bartender grins with his chin stuck out above the top of the white neck brace and asks, "Is this a test?”
Yeah, I say, it’s a test. Has he ever met Tyler Durden?
"You stopped in last week, Mr. Durden,” he says. "Don’t you remember?”
Tyler was here.
"You were here, sir.”
In this scene, the Narrator is beginning to piece together the truth about Tyler. At the very least, it’s clear that the Narrator doesn’t have a clear sense of reality. His lack of reliability disorients the reader, such that they experience the chaos and confusion of his dissociative state just as he does.
 
 
 
 
 
 
