The book is an area I'm still unsure about how much to guide the player. It's probably more than now. As it is, it's largely trial and error, though the words themselves are a kind of faux Latin, so once you get an idea what they do, it should be consistent. Additionally, most spells are three words long, with a couple four, a couple two, and one five. Finally, order doesn't matter for spells, only the words selected.
If any of this is helpful in figuring out spells, let me know and I'll work to better integrate them into the game itself.
Thanks for the feedback, it is appreciated.