Not sure anymore, how exactly the books are called, but since she sells only 2 it's easy to figure out by using quicksave/load.
One raises your attributes by 1, the other your abilities by 3.
Apparently, it was supposed to be fixed by now, but she still restocks the books each level. So if you don't use weird tactics to unlock her at lvl 4-5, you still should be able to get her @lvl 8-10, depending on how you play. It needs 5 star/bloodstones to get the room and that's the exact amount of stones you can gather on the Cyseal map....
Guess, there will be another hotfix incoming soon
