That novel's title character has the face of the dead Mathers, whom the narrator earlier killed.
This author created a fake author who himself created the characters of Slug Willard and Shorty Andrews, both of whom always ride off into the sunset. Another of this author's characters is known for his "melodious lays," which he recites even though he fell off a tree and bled "from head to toe." In one novel by this author, the narrator acquires a black box filled with four boxes of omnium. That novel's title character has the face of the dead Mathers, whom the narrator earlier killed. In a different work, this author intertwines the tale of the science fiction writer Trellis with that of Pooka by an unnamed student of literature. In another novel, this author wrote about an admirer of de Selby who meets Sergeant Pluck and MacCruskeen. For 10 points, name this Irish author who wrote the postmodern novels At Swim Two Birds and The Third Policemen 
This author created a fake author who himself created the characters of Slug Willard and Shorty Andrews, both of whom always ride off into the sunset.
Flann O'Brien or Brian O'Nolan