Speculative fiction is a broad umbrella category of narrative fiction referring to any fiction story that includes elements, settings and characters whose features are created out of imagination and speculation rather than based on attested reality and everyday life. That encompasses the genres of science fiction, fantasy, science fantasy, horror, alternative history, and magic realism.
Kris Longknife encounters some peaceful aliens
who have come to warn humanity of an unidentifiable force that is
roaming the galaxy, obliterating everything in its path — a path now
leading directly toward the human worlds.