eldritchhobbit

I don't actually agree with you about Frankenstein. Certainly it was an important early work. But an even earlier and also major work is Gulliver's Travels. It's primarily in the tradition of science-fiction-as-a-safe-language-for-social-satire, but that's a valid mode; many of Lem's works fall into it, for example. And I think it's SFnal in that Swift doesn't just handwave his giants being whatever size is impressive and narratively conventient; he make them so many feet tall, and so many times heavier than Gulliver, and tries to work out the consequences, and likewise for his other races—that is, he literalizes his tropes, in very much the way SF writers of later years do. I'd also note his crucial influence, for example, on Wells's The Island of Dr. Moreau, whose denouement is remarkably like that of Gulliver's sojourn among the Huoynhms.