The notes may be particularly valuable for Mathilde specifically, because a lot of her deeper knowledge of magic was informed by the Liber Mortis, which is fundamentally Vlad's understanding filtered through the lens of Frederick (at least as far as the magical side is concerned, the tactics and strategy bits have lots of Frederick). Pretty much every investigation into magic since reading it has been informed by that information.It's interesting that the 11 result, the highest roll, was "Chambers of Vlad and Isabella". And what we got from that was "study notes of the Carstein Ring". The 10 got the Scrolls of Zandri, and the 8 got the Creeping Flesh. Since higher is better, that would result in:
Ring Notes > Scrolls > > Creeping Flesh. But if you'd asked me to figure it out just from the descriptions, that's not what I would have said. I would probably have put it at Creeping Flesh > Scrolls > Ring Notes. I would have a prestigious volume for the Library is of high value, the Scrolls are a "this might possibly provide some actionable intelligence at some point, who knows", and a few von Carstein notes are a "nice to have".
I think probably the issue is me way underestimating the value of notes from a legendary master of magic on an artifact that just might have been created by Nagash. Notes that because they're on enchantment might help Mathilde improve her enchanting skills in ways otherwise blocked. Personal improvements, very powerful. Then for the Scrolls, I guess it's this line I should be focusing on. "Though they're named for the Prophecies that are the most famous feature of them, they also contain every errant thought that W'Soran gave voice to during the siege of Lahmia, making them a treasure trove of horrifically dangerous insight." Not sure exactly what sorts of insights to expect, and it will likely require at least two actions of language studies to take advantage (and only two because we took the Polygot trait).
EDIT: Looked up W'Soran on the wiki. Is basically the rule that the closer you get to Nagash, the more awesome magic is, and even insights filtered twice through from Nagash are better than any other human magic?
The Creeping Flesh is still great for the Library as opposed to Mathilde, though.
This (hopefully) sidesteps one of the big issues with teaching magic, which is actually communicating what you want. Mathilde would have an easier time working his insights for enchantment into her style than most others. And given how much the Liber Mortis did for her understanding, the enchantment notes are bound to be sweet too. If maybe not quite as extensive. But Mathilde is a natural talent for enchanting.