Without that first bit of research I did on this, I might not have realized what is going on, but O’Brien, at his own pace, handles that:
I was talking to a friend of yours last night, I said drily. I mean Mr. Trellis. He has bought a ream of ruled foolscap and is starting on his story. He is compelling all his characters to live with him in the Red Swan Hotel so that he can keep an eye on them and see that there is no boozing. (p. 47)
Metafiction–a story about writing a story. There are many things going on here, and O’Brien has indeed rather brilliantly tied them in together. Trellis is one of his own characters. Trellis intends to write about two of the other characters that our main protagonist has been slowly revealing.
Some of the things I’m noticing: The vivid descriptions of the main character’s characters appear to be in sharp contrast to his own physical demeanor; they are bold and strong whereas he describes himself as having "the feeble citadel of my body."
There is also the reluctance of the narrator to define his characters with specific status, and yet, his character of Trellis intends to actually compartmentalize them by putting them in rooms within his setting of a hotel.
I believe that O’Brien has carefully, very carefully thought out exactly what he wants to impart–meaning that there is a message within this, and it may be particularly for writers–and has put much time into coming up with the means to properly lay it out.
Amazing.