At first, I played and finished the game thinking I'd only be able to possess weapons. Imagine my surprise when I found out you could actually possess enemies and be able to use a second ability with each weapon!
I'd say the reason I missed this in my first run is that the game refers to the tutorial pathway as "Story", and the game also spawns you right next to the "START" panel. Since I wanted to experiment how the game felt, I naturally went towards "START" first. Making it more clear that that pathway is a tutorial could prevent people from missing any of that stuff.
I did also feel like the game could've used a bit of music as well. With that said, I like that all three weapons operate very differently from one another, especially the spellbook. Currently, there isn't much of an incentive to possess enemies, since staying as a weapon lets you continue attacking and you have a lot of health that way. The concept is interesting though, and I like the second attacks you get when possessing an enemy.
I also appreciate that you listed the controls in the pause menu. It's an appreciated touch.
This game has a neat concept, it just needs some polishing. Good work!