Nayoki repeats this wording exactly, watching Promise's mind with her Mindhealing Sight. 

It drops into place like a snare trap.

"Good. One more precaution. What sort of books did you get today?" 

"A couple more sorcery books and some atlases and field guides and novels."

"I am sure Leareth will be very curious to see them! Though - what language are they actually written in, you can read anything but humans are not like that." 

"They're written in plain text just like how I talk."

"Huh. Can I see?" 

Promise hands her a novel.

Nayoki peers at it for a moment and then flips it open to the first page. Can she read it? 

Yup. Long ago and far away, in a Queenless land, there began a creekpearl, and he called himself Infinity, begins the book.

Weird. Nayoki squints at it, then touches the page with a finger and tries to trace the shape of the letters - is it normal writing, with an alphabet and all? 

It's not harder to trace than Promise's voice is to hear as sounds and it looks like her native language.

"This is fascinating. I am so curious how that - works. Language that - is not language, that anyone can understand..." 

"It seems simpler to me than your way."

"I mean, it is simpler. And very convenient. Our way must seem so inefficient to you. It is just - well, it feels like a kind of magic to us, here." Sunspring gets up. "I will go see if Leareth is busy, he will wish to look at the books. What sorts of information are in fairy field guides?" 

"Identifying plants."

"Hmm. Do fairy plants have any magical uses - other than being effective for vassalizing mortals, that is?" 

"I'm not really sure what would be a magical feature of a plant and what isn't. Some of them make stuff you can turn into thread? They all... taste different? Some of them glow in the dark? Some of them can open and close their flowers depending on the circumstances?"

Nod. "I would not call those very magical, though glowing in the dark certainly sounds useful. Would those ones grow here, do you think? Without your using magic to keep them alive, I mean." 

"It'd depend! I'm sure there is some plant that likes the cold and also glows. I can keep an eye out."

Nod. "Thank you." 

Leareth arrives shortly later. He asks Promise if he can look at the sorcery books. 

She hands him one.

Apparently you do sorcery by holding in working memory a really ridiculous amount of detail about all the things already going on with the location or thing you are targeting. The book recommends starting with a fairylight and considering all the things affecting the amount and quality and directionality of light in your location, making sure you can pick out that exact location reliably without accidentally thinking about somewhere an inch farther off, considering the place's temperature and wind factor and dust content and air pressure and whether there's any sound that might vibrate the air and so on and so forth, and imagining in great detail exactly how your light will affect its surroundings. Apparently if you do this well enough you'll get a light.

Well, it's certainly very different from how Velgarth mages work. Leareth expects he'll be the best placed among his people to pick up the knack, though, he has the most varied experience and is unusually good among humans at deliberate concentration. 

He finds a comfortable place to sit in the library, stares at a corner, picks a precise point in space near the corner where two bookshelves meet, and one by one considers every light-related factor, everything affecting the air, and then tries to stack them up and hold all of it in mind at once, and - imagine a mage-light right there, like he's cast probably millions of times, except without casting it, just imagining in as high fidelity as he can what it would change about all the rest. 

It will take him a couple hours, and the light isn't strong, but eventually - there it is, a little point of white light just like Promise's.