Writers' Wednesday: What the Heck is Speculative Fiction??

So I'm working on a new YA (young adult) project, and in my browsing of the Web yesterday found this helpful website: YA Highway. Especially valuable is the "Field Trip Friday" feature, which seems to highlight the best YA stuff that's been out/talked about in each week.

I find YA lit interesting, I really do - the whole idea of your protagonist figuring him/herself out and taking on the world in the process. That's probably also an influence of my teaching teenagers. Despite all the attitude and all the hormones, that's exactly what they're trying to do too, and it's fascinating to watch and shape.

Having said that, I'm at a bit of a crossroads in trying to decide which genre my YA falls into, exactly. Very loosely, it's Shakespeare's Twelfth Night set in an alternate, post-9/11 universe, a la the television show "Fringe." It's not a dystopian society, which is what everyone seems to be writing and buying these days. It's just another, similar-except-for-a-few-key-differences, world. it's a world inhabited by people who used to live on Earth, so they've brought most of their previous life with them except for some changes they've had to make to actually live in a different world with a different atmosphere and different physical makeup. I don't think it's science fiction. I think it may be speculative fiction, but when I tried to find a definition of that I found about 20 of them:

'Speculative fiction is a world that writers create, where anything can happen. It is a place beyond reality, a place that could have been, or might have been, if only the rules of the universe were altered just a bit.'

'Speculative fiction stories, however fanciful, can have a big emotional and inspirational impact, teaching us much about ethics, bravery, kindness, good, and evil.'

'Some experts define speculative fiction as 'genre' fiction. A lot of readers think speculative fiction consists of science fiction and fantasy only. Other readers include horror, mystery and romance.

To me, it is writing that pushes the boundaries of the imagination. A good speculative fiction story would make you think, provide a new insight into human nature or even give you a new outlook on life.'

And so on...

Is anyone familiar with the speculative fiction genre? Do you read or write it? How would you define it?