If you want me to help pick holes in your book, it is one of my very few talents, and we can do it better in places that are not this forum. However, I need to answer a few questions.
Provided that at least some spells are cast via saying an incantation and sundry other requirements:
What happens if someone misspeaks the incantation?
What happens if someone does not know what a spell does, but casts it correctly otherwise?
What if some of the accouterments fail but the incantation and intention are correct?
How are new spells created? Is there a clear translation from intended action to incantation/actions?
Is the language of magical incantations syntactical, and is it well understood? Can people speak in the language, and does it have any sort of power in and of itself?
Is there a way to do everything needed to cast a spell physically and still not cast it? Does it require some control over magic, or is it able to be performed by any old luddite?
Where does the energy that powers spells come from? Is it biological energy made from ATP and pushed into some hitherto-unknown magic-organ? Or is it something like direct matter-energy conversion, and a person loses weight when casting, or is it drawn from ambient matter/energy, or pulled from other theoretical universes parallel to our own? [my understanding of quantum theory is not excellent, I apologize]
Can someone do more work than the energy present in their body is theoretically capable of doing, according to modern understanding of biology/quantum physics?
we'll start with that, I suppose
This is also assuming that spells can be manipulated by magical aptitude, or magic can also be done without incantation