If the fantasy genre has its roots in fairy tales and mythology, science fiction birthed from the horror genre in a kind of mutated mitosis. That relationship is on prominent display in HG Wells' The Island of Doctor Moreau.
is how it came to be added to my reading list. However, to be more specific, it is one of the earliest works of Gothic horror, more a precursor to Mary Shelly's Frankenstein than it is to The Lord of the Rings. That is not a genre that I tend to favor, but the idea of reading an early work of speculative fiction was intriguing to allow me to look past that element.
For our purposes in talking about framing stories, we will define the story being framed as the plotlines explored directly by the narrative. To take a well-known example, look at Harry Potter. The plotlines of the character arcs, and combatting Voldemort, are the core story. A framing story could be if there were a line at the beginning or end of the books saying "based upon the diaries of Harry Potter, Wizard." Which takes us conveniently to the next set of definitions we need to supply.