I should note that this rebuts the idea that long-form fiction is disappearing, it's just not getting physically published, because the internet remains the best way to distribute information (and often make a living, since patreon can often end up paying more than a publisher).
Seems like we both got very similar book tastes. And to recepriociate, I think you might enjoy: - Pretty much everything by Ted Chiang, but especially Understand - Asimov's Nightfall - Greg Egan's Reasons to be happy
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.