There are some skillbooks which never appear on vendors.
I've personally ran into not finding:
Dust Devil
Whirlwind
Walk in Shadows
I've used the save/reload trick dozens of times and never have these appeared. A little internet search found a few forum posts on other boards with people having the same issue.
Is this intended or a bug?
Can't say for everyone but I've bought them all. I was looking for Flurry for long time but got that later on as well.
I was a noob and didn't know that we could make spells
