I re-read At Swim-Two-Birds, since I had it in my office. I remember a paper I wrote in Grad School on it, for Albert Guerard. He was champion of postmodern metafiction, but somehow this novel did not resonate with him at all. He said it was too close to "standard realism," which I found a bizarre judgment. Guerard also said I used too many clichés in my writing, which I suppose might have been true at that time.
Now you can not like the novel for any number of reasons: any reason except for that particular reason, that is. I probably discovered Flann O'Brien from Frank O'Hara or Gilbert Sorrentino. Sorrentino's Mulligan Stew is obviously inspired in part by At Swim-Two-Birds. The idea of a novel within a novel within a novel, with characters rebelling against their author.
I interpreted the novel as Bildungsroman. The narrator ends by seeing the humanity in his uncle, who previously was seen as figure of ridicule. He passes his exams and the uncle gives him a watch as a present. The metafictional writing becomes a mode of self-discovery. I don't think I have the paper any more. My friend at the time Joe Conte also wrote about it at some point in grad school and published an article, if I am not mistaken.
I went on to read The Third Policeman, possibly even more brilliant than ASTB, and virtually everything else he wrote, but haven't been re-reading him in the ensuing years. O'Brien, whose birth name is Brian O'Nolan, wrote a lot in Irish for newspapers, satirical columns which have been translated into English.
Now this kind of metafiction seems a bit cliché, but it was not cliché when O'Brien did it. He was writing this when Calvino was still doing "standard realism." It was published in 1939.