Are skill books not needed after big bang?

Those aren't skillbooks, they're mastery books. Those stay.
Skill books from Zakum stay. All other skills except Hero's Will are given to you, so no more questing for skills (except Hero's Will).

Are you saying you wont need to do quests for any other skillbooks expect the ones that come Zakum?

Wow, so very fair when Aran gets literally all skillbooks from Zakum.