I have a theory, too. Here's an explanation of why some people can see ghosts and use libris.
When I asked if there are any factors that might influence whether this happens to someone, I got this.So, in the book it is this big mysterious thing that certain people only get tiny glimpses into, and there are so few people who can do it (and their abilities so negatively looked on) that there's very little research or knowledge about it. They know they can do these things, but not really why. But the more specific explanation is that there are these two worlds that are essentially right next to each other with some overlap (which is why ghosts can be in the living world and things like that). Because of that overlap, what happens is on very rare occasions someone will be born into both worlds at once. People like Maaya and Adelaide.
It's a very lopsided ratio; that is, only a very tiny sliver of them is in the other world. But the more a person is a part of the other world, the more they can do. People who are very powerful with libris, for example, are more a part of it than someone who only gets strange feelings when ghosts are around.
That last part especially. We know that Adelaide is neurodivergent and that she struggles a lot with things, and I don't want to take away from this with a supernatural explanation, but we also know that she's one of the strongest libris elites in the entire country based on what Sanna says. That much power might imply that more of her is in the second world, which canonically seems to "mess with [a] person's sense of reality," which we know is something Adelaide sometimes experiences. So I wonder if these things are connected, even if it wouldn't explain everything about her.It's mostly chance, honestly. There's a small chance for it every time someone has a child, and nothing that really influences that chance. As for power, that's also *mostly* up to chance, but people born during certain times of year are more likely to be farther into that world because during certain times of year the worlds are closer to each other. Maaya's an October birthday, so that could have influenced her. Adelaide's a June birthday but... well, she's Adelaide, so. >_> If someone was born more even between the two, though... I honestly don't know, but I don't think they could survive in the living world. The closer you get to the other one, the more powerful you can be, but it also becomes more dangerous. At a point, the overlap would be too jarring and probably mess with that person's sense of reality and their ability to live at all.
Also, for those who got the paperback, did you see the design on the back? I really like it. I think it's supposed to be a libris design, but using elements of both Maaya's and Adelaide's card designs.