@Kimstu ninja’d me. The concept of a literary “canon,” which favored certain literary works above all other writing is yet another legacy of the Victorians, like the nonsense about usage and grammar that was drilled into a century of schoolchildren. It skews everything people think they know about fiction.
Mass market popular fiction developed in the mid-19th century, as soon as high speed rotary presses were common. These “shilling shockers” (Britain) and dime novels (American) were violent, fast-moving, filled with stalwart good guys and loathsome evil villains, plotted to ensure a happy ending, and utterly formulaic. Most modern genre fiction (“bestseller” is a literal genre: multiple books on “how to write a bestseller” exist so that everybody can aspire to be Dan Brown) follows those principles almost exactly.
The literary canon has changed over that period, but even terms like the Lost Generation or the Modernists don’t yield easy summaries. Can anyone compare Hemingway to Faulkner, Fitzgerald to Mann, Salinger to Dreiser and find commonalities?
Literary fiction outside of what we remember as the canon - and some inside it - was undistinguished and nonexperimental. Examining bestsellers lists over time finds page after page of authors nobody remembers. (Warwick Deeping hit the yearly ten best selling books list four times in a row in the 1920s. Anne Douglas Sedgwick did the same non-consequtively. Hemingway, Faulkner, Dreiser, and Fitzgerald? Zero.) How were those books written? I don’t know, but even people who try to revive forgotten stuff don’t bother with them. And this is true for at least the first half of the 20th century and sporadically for much longer.
Bestsellers as a genre changed the market. Peyton Place prefigured supersellers in the 50s but I think the real takeover was in the 80s, with Judith Krantz, Sidney Sheldon, Jackie Collins and the others. Big fat books that gave more to the dollar.
I read the NYTimes Book Review. At least half the fiction reviews are of books like the aforementioned Lucy Ellman. Experimentalism is back in, at least among the tiny sliver of Americans who read such books. (Which is not me.) But book sales are overwhelmingly of genre books. Some genre books are literary, to be sure, and standards have been raised across the board, but formulas abound.
Although, if you want chapter-long digressions about technical topics without humans, hard science fiction provides more of it than Melville.