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?
It is probably intended.
Anyway, you will have access to all the skill books of two specific skills of your choice if you follow the story. So be patient.
Hint:
Save before you are asked to choose an elemental in the homestead.
Another hint:
you can also create your own skill books if you have 5 crafting
