First time a character clicks on bookshelves in the game, I get some nice skill ups. After that, it's no skill ups or just one from checking all the mage guild ones.
I have tried adventuring/questing in another area. Waiting for over a week. Still pretty much nothing but a rare increase in something like provisioning.
Then I get surprised weeks later when that character gets several skill ups in a row from bookshelves in a dungeon.
So, exactly how does it work with bookshelves? When is it worth checking them again once you have done the initial check on a new character?