So yes, I’m very privileged. I got to read Every Heart a Doorway a long time before it came 
out. And now I’ve had the chance to read the prequel a long time before it comes out, too. It’s out from Tor.com on 13 June 2017…
The blurb says
Twin sisters Jack and Jill were seventeen when they found their way home and were packed off to Eleanor West’s Home for Wayward Children.
This is the story of what happened first.
Jacqueline was her mother’s perfect daughter—polite and quiet, always dressed as a princess. If her mother was sometimes a little strict, it’s because crafting the perfect daughter takes discipline.
Jillian was her father’s perfect daughter—adventurous, thrill-seeking, and a bit of a tomboy. He really would have preferred a son, but you work with what you’ve got.
… and the opening, which is set in the Real World, is about the most horrifying part of the whole thing. Parents who have children because they think it will make them look good, who force children into preconceived notions and potentially do a lot of damage: it’s just hideous. And the worst part is the way that McGuire writes about this from a very knowing, self-aware position: the narrator is pointing out what the parents are doing, making sure the reader knows how dreadful this is. And it works to heighten the horror rather than defuse it; this is not ‘telling instead of showing’, this is a sympathetic yet almost malicious commenter making sure you know exactly what’s happening.
Then the twins find themselves in a different world, and they get to make choices for about the first time ever and those choices have serious implications. And the way they’ve been brought up has consequences for the choices they make, and also doesn’t in the slightest prepare them for them.
I can’t tell you how happy I am that Every Heart a Doorway wasn’t a standalone story. And this is an absolutely standout addition to the world of portal fantasies that McGuire created there, with Other Worlds matching the people who find them and having an irrevocable impact on the inadvertent travellers. I love how McGuire takes bits of other stories and fairy tales and weaves them into her story in her very own way: you get the pleasure of recognition combined with the shock of difference and it’s a delight.
Apparently there will be a third book. I’ll just be over here, watching my inbox, waiting…
Randomly Yours, Alex 
[…] Down Among the Sticks and Bones is a prequel to Every Heart A Doorway ; this is Every Heart’s sequel, chronologically speaking. You could absolutely read this without reading the other two (although seriously, why would you not read Every Heart? It’s one of the best novellas I’ve read in… years); there are some spoilers for Every Heart in Beneath the Sugar Sky, because there’s passing reference to the events that occur, but they’re not enough to make this novella opaque. […]