Non-arcane forms of magic are accessible only to Abraxas-native Daemons and Fey, so Thorne's library wouldn't have anything about them other than brief mentions of their existence.

Characters can learn multiple branches of magic, but although we aren't asking players to keep stat sheets or anything like that to track their magical progress, most mages spend years and years mastering one branch of Arcane magic. For PCs that is sped up a little to around a year to fully master it (because of the Singularity and because us mods don't expect you to play for years just to master a branch of pretend magic) but if your character wants to master a branch, they should stick to one (although they can practice but not fully master another branch on the side if they're willing to learn their main branch a little slower; think of it like a college major and minor). If they want to be a jack of all trades, they can, but will not attain as high a level of mastery as a focused character.

Note that learning a little bit of magic in one branch doesn't lock you in to that type of magic, so if you decide to change directions or already have another branch of magic in mind that is fine, it's only when your character would start to be notably proficient that it'd be more difficult to change course.