Omg this was so cute???
It does suffer from the usual YA problems like underdeveloped characters and a predictable plot, but otherwise it’s unexpectedly good. 
Susan, the MC, is very much the "chosen one" with special powers and special parentage but it’s not annoying and they don’t make her overpowered. And she’s punk!
Merlin is a delightful love interest. Loved the approach to his gender and how the fact that he’s questioning it doesn’t make him any less attractive, flirty and self-assured. Again, I would have loved a bit more elaboration on this topic, but maybe we’ll get it in the next book. 
I thought at first that the constant clothes descriptions would annoy me, but the ended up being a really fun detail. 
The worldbuilding is interesting but sparse. Not developed enough. 
Overall, very easy and light read.