Well i've fallen victim to the restoration mastery bug (a long long time ago) and therefore can't buy that damn thing from Collette (... one may assume Beth attempted to fix that by now but no of course not)
Well back to topic: I remember i found a Flame thrall spell book inside Apocypha (not sure where exactly but i found one). Now i wonder if it's possible to find the other mastery books too.
Also: Does Apocypha respawn/reset loot? And if so how long do i have to wait approx? --- Hey i'm not camping ... i'm "tactically waiting" :-D
The Flame Thrall book is hand-placed, but we've been able to find others. I made a topic about them after Dragonborn came out, you might be able to find it. --- Hey! Who's that thinkin' nasty thoughts?