Every Heart a Doorway is simply beautiful.
The premise is a boarding school for teenagers who have gone to other worlds, fantasy worlds, and then returned, and are left longing to go back to the place they now feel is home. They need a school (run by someone who had the same experience) because people in the mundane world don’t believe them and can only try to force them to fit the surroundings where they don’t belong. Naturally the overriding mood of the story is wistfulness, and it’s perfectly captured.
The main characters are tremendously appealing (yes, even the amoral mad scientist); they are a group of clever misfits who support each other fiercely, although recognizing that they can’t provide a true home for each other — Nancy reflects that “this was the place where she came closest to belonging in the world.” The idea proposed about the otherworlds is that they are attracted by “sympathy” to people who are already out of place in their lives (to be sure it doesn’t always work out perfectly — not all world-travelers found themselves in a place where they would happily stay forever). That’s the reason that the vast majority of the students are girls, since they’re much more likely than boys to be disregarded and expected to squeeze themselves into a corner of the world rather than having the world shape itself to their wishes.
The main character is Nancy, who traveled to the Halls of the Dead, a place of ghosts that resembled the painter John William Waterhouse’s shadowy groves. (So many of the fantasy worlds described seem (at least in aesthetics) like ones we’ve heard of previously, that I wonder if the author means to imply that this world’s artists are depicting actual otherworlds.) Not only is Nancy asexual, making her need to conceal from her fellow high-schoolers that she doesn’t, like them, find mating games to be the most important thing in the world, but there is just a fundamental mismatch in the, you might say, energy of how she exists compared to everyone else, and the stillness of ghosts is perfect for her.
There’s also Sumi, a charmingly, chaotically energetic girl who escaped a very rigid and prim family to a nonsense world. And there’s Jack, a twin who says “Our parents were… the sort who always wanted to put things in boxes…. Ever watch a pair of perfectionists try to decide which of their identical children is the ‘smart one’ versus the ‘pretty one’? It would have been funny, if our lives hadn’t been the prize they were trying to win.” Jack went with her sister to a world of horror where she became apprenticed to a mad scientist, where the question was not what ought to be but only what could be, namely anything. And a number of other equally vivid characters.
It’s a short novella, and it’s just the perfect length. I don’t think anything needed to be added to flesh out its themes and characters; it says what it had to say and ends on the right note.