In the article I co-authored with Michael Shanks and Bill Rathje, I included great swathes of Russell Hoban's fascinating 1980 novel. For an example, see the page on Archaeological Excavations of the Future. There's a lot more to the book than this account of an excavation (it's not really archaeological in the modern sense -- it uncovers past remains for the purpose of salvaging scrap material). I'll expand on this a little later but, for now, you'll have to make do with an interesting looking link:

Riddley Walker Annotations.

I'm sure that there are plenty of people out there who wouldn't call this Twentieth Century Science Fiction -- mainly the sort of people who'd argue that it's good, and SF isn't -- but that's the category I'm putting it in.