Of course Flann O'Brien (or more precisely Brian O'Nolan) is a pillarstone of modern Irish literature and whatever critical remarks I make, will mark me as a nincompoop. Jim Norton's reading style did not help much to reduce my frustration with the story, because he appeared to work on a new speed record in reading. Naturally there was little color and nuance in the fast talking.
There is some humor in Flann O'Brien's aimlessly meandering narrative, but I would not call it dark, as some professional reviews say, to me it seemed to be simply infantile. Flann O'Brien seems to be obsessed with the childish question and answer game, we know from Rumpelstilitskin. I have a hard time to believe that there are readers around, who would not want to push the fast forward button, when a dozen or more times somebody asks for the profession or name and the answer is unwaveringly: "No, that is not it"
Yes, the story is bizarre and grotesque, but not very original. Monty Python does a much better job with bizarre humor by the way. The Third Policeman is not only lengthy, repetitive and boring at times, even worse, it can get on your nerve to listen to lengthy footnotes in a ficticious book of a ficticious author or the endless and detailed description of a box, which contains a smaller box, which again contains a smaller box and so on for 29 or more times.
Without giving away too much the storyline is as follows. A nameless orphan, who lost both his parents in his early childhood, becomes obsessed with the writings of a ficticious De Selby. He becomes so engrossed with De Selby that he lets the farm and the public house, he inherited, fall a part and spends all his time on writing commentaries on De Selby. To solve his monetary problems, he finally decides to kill and rob an old man. The killing itself is quite brutal, but the loot escapes him. To regain it, he goes to the police, where he learns about the atomic theory, the world being a sausage and people turning into bicycles.
If you really have too much time on your hands, read the book and form your own opinion.