As a serious student of literature I changed my concentration while in graduate school from being a Medievalist to a study of the dramas of the Restoration period in England. What interested me then, and what continues to interest me, were the artificial conventions used on the stage to develop the narrative, link together the action, keep the audience aware of the interweaving plots, etc. Specifically I was smitten by the convention of the aside.
Follow the thought: a character in a play steps to the front of the stage and lets the audience in on a secret that quite possibly the rest of the characters on the stage are unaware of or makes a comment about the play as if the actor isn’t in the play themselves. Is it such a leap to Federman’s characters stepping out for drinks when the author isn’t around? How about At Swim-Two-Birds: if memory serves, there are at least three layers of artificiality in Flann O’Brien’s fiction. The unities of fiction were deflated long before the advent of the postmodern writers.
Start with Laurence Sterne. If you haven’t read Tristram Shandy at least once, turn off the computer and go directly to the bookstore for a sturdy copy which will withstand numerous re-readings. Sterne sets out to write the history of Tristram Shandy, much like Fielding wrote the history of Tom Jones, but Sterne discovered that a life doesn’t follow a regularly ordered sequence of events but rather is just one of the many events in a multiplicity of events going on all around the focus of the history. So, Sterne starts with the birth of Tristram but almost immediately branches out and doesn’t get back to the life of Tristram Shandy for well over half of the book. The artifiicial convention Sterne used freely in his writing was the digression. He was so enamored with the digression that he often digressed within his digression … and didn’t even stop there.