The skill books that spawn in The Teller Of Secrets inventory every time you level:

IT IS NOT an EXPLOIT
IT IS NOT A GLITCH
IT IS NOT A BUG
IT IS NOT A CHEAT
IT IS NOT ANYTHING OF THE SORT

It's nothing but a normal function of the game called A RESTOCKING Inventory like anything else.

I don't see people saying her restock of Pixie dust is a glitch.

It's an unintended feature... which is pretty much the definition of a bug.

Hey look its another tx3000 thread. I can't wait for 5 pages of replies of people arguing about the definition of 'glitch' and tk3k failing to listen to reason.

Divinity:Original Sin Patch v1.0.72 It is a bug, because the developers meant to change it yet failed to actually do so.

It's unclear whether or not it is an exploit, glitch, or cheat.

For what it's worth, I'm glad it didn't actually change. I don't agree with the decision to remove regeneration from the books.

The only bug is when it regenerates w/o you lvling up. Idk how that happened but it happened once.

There's also a respawn every 24 hours I believe.

So which is it?

Is it suppose to be 1 book per level or only 1 book?

I believe that according to Larian it is intended to be 1 book period.

I refuse to co-op with people who abuse the Secret's vendor, it makes the game boring.

According to the patchlog it is not an intended feature regardless how you want to call it.
Just think about the balancing problems regarding the mass of additional points and the power difference between parties that unlock this portal at different levels (the lvl 5 SoS rush vs the guy that saves all his Bloodstones and unlocks the Seller at lvl 15).
That being said, I would like to see these Books getting changed to give the bonus points to each member of your party, so that players don't have to "fight" about them in co-op.

Tx3000 misses the point and is totally wrong again...

More news you already knew at 8.

(I do agree with eideon btw... though seeing how without this exploit there are about 5 of these books in the game (3 stat, 2 ability) that might still be overkill, might not be...)