The issue is related to the "phantom spellbooks". Or rather "spells dummies". Those have been around since release and probably longer.

It seems during developement the developers had several dummy spellbooks, testing, adjusting things and so on.

Now, a few weeks after, there are more and more reports of players noticing those dummy spells appearing and being available for selection. Problem is, that they most likely can break your character save file, if they are not treated correctly.

So it seems the developers wanted to tackle it, but got interrupted midway. For a short while there was even a development build accidently released on Steam, the 1.0.7d which called out for the 1.0.7e since there were very huge issues with that build.

Somewhere along the way the phantom spellbooks became entirely visible. And they tried to hide it again. Apparently that got messed up with working spellbooks. And now they need to fix it anew from ground.

No guarantee that is entirely correct though. It is a sum up of my observations around the versions which have been released yesterday (3) and the comparison of the phantom spellbooks when you could see them. I welcome any correction from the developers who actually know.