A police procedural and confessoin from a naive narrator in a novel like none other

Interest sparked by a (review of) new biography of the pseudonymous Irish writer Flann O'Brien, I've picked up my old copy of his (posthumous?) novel, The Third Policeman, and begun reading (years ago I read his most famous novel, At Swim-Two-Birds and all I recall of it is that I thought it was strange and funny). So far, Third Policeman is also strange and funny, and like no other novel I've read. It's narrated by a man who is the extreme case of a naive, perhaps therefore unreliable, narrator, and he begins by telling us how and why he murdered a guy named (I think) Mathis - so this novel is structured as a confession, perhaps to the police or authorities?, not yet clear. The narrator describes his obsession w/ a philosopher (not a real one - can't recall his name at the moment) who has written many treatises on his odd theories such as darkness at night is a result of black-colored winds that arise in the upper atmosphere. The narrator takes these and other theories seriously (as does O'Brien; the novel includes footnotes about various commentaries on the theories). The narrator also explains how he has hired a man to help run his family farm and pub and how much the man has helped him - when it's obvious to us that the man has swindled him over many years - and ultimately the man gets the narrator to go alone w/ him on a plot to kill and rob a wealthy, reclusive neighbor; again, it's clear to us that the man has set up the narrator while making off himself w/ all of the plunder. The narrator sees none of this. So this is something like a Mice and Men as if narrated by Lenny; as we read we keep thinking, oh, you poor guy. And yet - it's all very funny, not only because of the crackpot theories of the philosopher whom the narrator has studied and written (he hopes to publish a book, and his motive for participating in the robbery/murder is to get money to do so) but also because of the narrator's quirky self-expression - a police procedural perhaps, but like none other. Not sure how this will sustain over 200 pp (I'm about about p 40), but a good start.