Really awesome game ! I really like the mechanic to cast spells. I got pretty lucky on my second playthrough since i got the magic revolver spell XD. I used it to deal with pretty much every enemy. Some spells are way more OP than others, though it should be just a numbers issue. Each one is still fun to use, though.
That said, I think it could be nice to have a quick note that can store 2 or 3 spells so players can look up certain spell combinations quickly. Of course, this depends on what direction you want to take the game, but having a memory aid can be really helpful for some players.
Overall, awesome and interesting game ! Enjoyed it really much.