Paul Auster
The first story, "City of Glass", features an author of detective fiction who becomes a private investigator and descends into madness as he becomes embroiled in the investigation of a case. It explores layers of identity and reality, from Paul Auster the writer of the novel to the unnamed "author" who reports the events as reality, to "Paul Auster the writer", a character in the story, to "Paul Auster the detective", who may or may not exist in the novel, to Peter Stillman the younger, to Peter Stillman the elder and, finally, to Daniel Quinn, the protagonist.