Earlier quoted context omitted.
That was my first thought. Maybe it’s not “books are getting shorter,” but “publishers are getting cheaper.” Decreasing margins, decreasing font size, etc could all explain a diminishing page count to save on printing costs. That said, from looking into publishing, it seems like consensus is anything over 100k words (approx 400 pages) is basically unsellable unless you’re Stephen King or something. It’s not clear to…
Many of the longer novels in classic literature were originally serialized, and only later compiled into the lengthy tomes we know today.
Earlier novels (relatively few in number) tended to appear as their own works in whole form, so far as I'm aware. Though many may have been adaptations of other works --- sagas or legends (e.g., the Faust legend), plays, and other forms.
https://en.wikipedia.org/wiki/Serial_(literature)>