Alternate history: SF, Fantasy, or Something else?

Over at Tor.com, Jo Walton asks this question and a lively discussion has ensued.

For most of its time on earth--at least, this version of earth--Alt History has been considered science fiction. Now, folks are thinking it ought to be given it's own genre title, "Alternate History" under the broader genre term of "Speculative Fiction." I'm inclined to agree with this sentiment. I like the term speculative fiction because it encompasses a broad range of genres and tropes: SF, fantasy, horror, alt history, etc.

Honestly, I think this kind of discussion started as a result of Michael Chabon's wonderful alt-history book The Yiddish Policeman's Union. He's not a SF writer, he's a literary writer with SFnal leanings. The mainstream public read the book and probably didn't think of it as SF. Yet, it won a slew of SF awards. So it much be science fiction, right? Well, not so fast. It was also nominated for an Edgar, the awards given for best mystery stories. It *is* a mystery, after all, but it's set in an alternate universe. So what is it really?

It's more than one thing. That, to me, is most important. It's just a book that amalgamates many tropes into one single thing: an enjoyable novel.

What does this all mean about genres and tropes and labels? Don't know. But I will make this point: with my viewing and reading of Charles Dickens this spring, an obvious thing emerged. Your typical Dickens story had the tropes of many different genres in the same book. Since there weren't genres labels yet, Dickens' stories were just that: stories. Genres are labels that are good to have for marketers and readers, to be sure. If I want a cozy mytery with cats, I know where to go.

But what about just good stories, regardless of label or genre? Who really cares on what branch alt-history finds itself on the giant tree of fiction? If it's a good story, it's a good story. If the story involves witches or serial killers or soldiers or astronauts or four women living in NYC, read the story (or not) because you want to. Fiction is supposed to be fun. And alt-history is really fun, no matter what genre it is.

How about you? What do you think of alt-history? Where should it fall?