Aw no books on magic. And he can't even sneak out and look for some somewhere else. He'll figure something out! Maybe other Jiang Cheng will bring him books if he asks politely. (...And can figure out how to ask for the specific ones without being really suspicious). He'll figure it out!
He's curious about other him's poetry but he'll look at that later. He laughs when he sees the Lan rules, a sudden feeling of connection and right-at-home with his other self. Of course no version of him could get through being at Cloud Recesses without that. He wonders if the rules are the same but he can check that also later. Other him's pornography! Also curious, also later. He can save that for after punishment.
And here are other him's notes! He throws himself on the bed with the pile. If he was feeling like being organized, he could try to sort them before getting into reading in some kind of order. Which is to say, Wei Wuxian dives right in in whatever order he happens to see things or spot something he wants to look at immediately.
Shopping lists: good for seeing what sort of things this world has. People's names: possibly good for seeing who else this world has that he knows versus doesn't know, if the names are familiar at all. Math equations: he attempts to use them to guess at what math this world has. He has no idea why other him was interested in trees (or if trees are magic) but puzzles over it a little in case he can figure it out.
Aw bunny, he pets the little doodled bunny. The other Jiang Cheng doodle is a bit weird to see. Not that he hasn't drawn his own share of Jiang Cheng doodles that would not go great for him if his brother saw them! But - he can't quite put his finger on it. But, this Jiang Cheng does probably run around more than his does, what with the jumping. Lan Qiren! Of course Lan Qiren is looking disapprovingly at Wei Wuxian spilling ink around, some things can't change.
Lan Zhan!! He's so glad to see Lan Zhan!! He wants to meet other universe Lan Zhan. ...Do they really do that with swords here. He wants to ride on a sword. Shijie! And there's an other Nie Huaisang too. (...He's still worried about what other Jiang Cheng had thrown out about Wen Ning but he's not going to figure it out from a picture of him so he will think about that later.) He spends a little time trying to compare little Lan Qiren and Jiang Cheng and Shijie's robes and hair against Lan Zhan's and Nie Huaisang's and little other him's to see if he can figure out the local signifiers, but isn't surprised when he can't; other him isn't doing commercial illustration anymore than he does, no reason to be sure to draw those in.
And, magic! Complicated and assorted works in progress or pieces of the same are not exactly what most people would consider the best material for learning an otherworldly magic system, which isn't going to stop him at all. He takes more notes, traces over pieces with his finger, tries to make out the margin notes. (Other him does magic! The well of course he does and the delight for the other him mix up under his more momentary feelings as he makes his way through notes).
Reference copies for finished things are great and very useful for him. His own pile of notes grows some more. (Also, the artifacts before were suggestive but at this point it's basically certain that this world has desired-instructions type magic and Wei Wuxian is very excited about this). He does not try drawing out any not-notes paper artifacts and sticking them to a wall like other Jiang Cheng had, or try any other 'can he make this work' ideas coming to him. It probably wouldn't work, and if it did work that would be worse, no Wei Ying.
...That is. Not what he was expecting. (...Is that why Burial Mounds). Right, ok, energy-from-the-dead magic. Is all the magic like that? Do you need to not bury people properly nearby if you want to jump on a roof? What he was getting from his senses for power before didn't feel like that was happening, but how would he know, it's not like he has a basis for comparison.
He also doesn't try playing any of the music. Even though it wouldn't do anything directly and he could play very quietly. So much magic and he can't even try it out, this world is very unfair to him personally. Next time he gets randomly teleported he wants one of those worlds where he has to immediately do a magic tournament. He takes notes on the music, and does lift his flute to his lips, tracing out the finger motions in complete silence.
Wei Wuxian is definitely going to be absorbed in this for long enough that unless Jiang Cheng was incredibly off in how long he'd be away, it'll take up the rest of the time before Jiang Cheng's return.