The spells system is great. Had a few bugs pop up though.
Bugs
Like when I died in test-build B holding a meteor book and once I respawned, the book got sent to my inventory yet I still had the magic power. While that was happening I equipped a kinesis book and I was able to use both powers. It was honestly really cool actually, to hold an enemy up and fire a meteor on them and send them flying. Only happened once though.
Everything else is good though. The only thing you could add towards the spells are well.. more spells haha.
Ideas
If you need some ideas.. hm have you thought of a mutation spell? Some sort of thing that mutates an enemy or few like that one debug spell.
Jo0ce said something about those rainbow lazers Mrs.Slitherss fires. I agree with that, it's pretty sick.
Really just trying to think of something already in the game in some form. Hope I could help in anyway.