About forty years ago, I watched an hour of "Firing Line" in which Leslie Fiedler was the guest. He spent most of fifty minutes explaining to William F. Buckley, Jr., that he considered the distinction between popular and high literature to be false and misleading, and why he thought this. I'm not sure now whether I agreed with him at the time. But I thought that he had made his position entirely clear. Fiedler wrote and spoke well, and Buckley's questioning gave him full scope to clarify anything one might have misunderstood.
On "Firing Line" there was always a panel that got to ask questions in the last ten minutes of the hour. The panel this time was made up of professors of literature from a local university or local universities. The first question any of them asked was, "Well, then Professor Fiedler, how would you distinguish high from popular literature?" At the time, I was astonished, for I had not yet learned the extent to which adults will not listen to one another. I am still surprised, since these men were put in front row seats for the purpose of listening to the conversation in front of them, and responding to it.
On reflection, I think that one can distinguish the purposes for which works of literature are written: the market, self-expression, forging the uncreated conscience, etc. However, it is drearily clear that much literature created with the best of motives is immediately or soon unreadable. And much literature that once qualified as popular literature--Homer, Dickens, one could say Tolstoy--remains worth reading and re-reading.