Hmm. 
Well, it does get better as it goes. But that's not to say it gets particularly good. I found myself either laughing at parts that were not intended to be funny, or cringing at parts that were meant to be meaningful. Apparently it was too hard to decide on a trope so... take them all, I guess.
It's a cute little pg fantasy romance that's very fast-moving, and would probably be fun for early teens? The problem is that there's nothing unique about the story and it really just takes a few tropes and glues them together rather than telling a real story. The plot is not bad, it's just... meh. As fast as it seems to move, nothing really happens. 
There is no world building or character set-up. The reader is thrown in straight off the bat. It still makes sense because it's fairly simple and easy to follow, but feels very off-kilter because everything's ironically serious. At first I genuinely thought I was reading a sequel and just missed the first book. 
Quell is very ignorant and childish, and everyone around her is blind to her very obvious secret. Even after the end of the book I can't tell if she is a true protagonist or if this is a villian origin story. I could see the series moving on in two opposite directions- dark magic is actually good if you embrace it, or the bad people of good magic forced her to choose dark magic which took her over and made her the supervillain of her time.

This book definitely reads like it's aimed for mid-grade reading level. It's classified YA so I didn't expect it to be super complex, but I've read other YA that is extremely well developed and intriguing, so I don't really think the age of the aimed audience is an excuse. I got more interested as it kept going, but it's rather unimpressive as a whole.