Oh, most of anything before the 1900s. Although those creep in too as English Literature class I taught included The Great Gatsby which is the 1920s. It might be anything with a publication date older than 1980 now.
Science fiction is a genre that focuses on pushing whatever scientific knowledge that's happening that might also be labeled as speculative fiction. The forerunners were Mary Shelley, HG Wells, and Jules Verne. It tends to now be more focused on space travel and people you might find out in the heavens.