This book starts very slow and isn't set up to make a whole lot of sense. The world building isn't great. The history, magic, and terminology isn't well explained, to the reader or to the main character. I felt pretty meh about the book for at least the first third of it. 
However, it gets better as it goes. From the beginning, Sel was the only character I liked / felt interested in, but the friendships develop with time, and I got used to the slightly confused feeling lol. It took a while, but the main character grew on me a lot. 

The audio narration is pretty good, but reinforces the fact that the narrative is coming from a teen. There's lots of cliche stuff thrown in for drama and the immaturity of the reactive characters bleeds into the writing style since you're getting into their heads.  I saw reviews saying this book is less YA and handles more as PG-13 adult fantasy, but it really does not. It's YA in writing style, topic broaching, and depth. That being said, I do like to sprinkle YA into my reading and I probably enjoyed it more because of that aspect of it. I get sick of adult romantasy if I read too much of it. Reading innocent books can be a relief.

I simultaneously loved the excalibur part and got very confused at the same time. After that long book I still don't understand the magic systems, or when or how we got to reincarnated Arthur and Lancelot (as well as a long-term possesion by grandma at the same time??). I definitely got to the point of just accepting whatever came at me with this one. Is the main character now supposed to be three spirits inhabiting the same body? Guess we'll hope for clarity and maybe a reason why in the next book.

I'll keep going with the series :) 
^if there's any SEVENTEEN fans out there, appreciate that I could only think of DK ⚔️