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.
"A strange and brilliant book that has never received the attention it
deserves, partly because it strikes eternals through a child, yet is
not a children's book." – Bleiler, The Guide to Supernatural Fiction