Actually, I should have mentioned that resurrecting NPCs involved in cutscenes can cause problems:
Hostile traps / summoned / resurrected creatures.
BTW, I found Kistandalius (or less often Blake) in Ars Magicana and Corinna (or less often Mpenzak) in Verdistis to be the best sources for purchasing spell books, though most NPCs have a chance of carrying one.
