The plot and general story idea had so much going for it, but I feel like it fell a little flat. (Of course, this is my perception of the book; a different reader may have had a different experience, but I, personally, did not enjoy it.)
To start with, the little teaser on the cover: "How do you find your soulmate when you don't have a soul?" drew me in; I was like "Ooh, soulmate AU? Count me in!" It was not a soulmate AU (which I did adapt my mindset to consider). While there was romance, it was very minimal, and even could've just stayed a friendship and nothing would've changed.
Additionally, the title is deceptive. Iris isn't a "girl with no soul," but rather "a girl with a missing soul."
In the end, I wasn't emotionally connected to the characters in any way whatsoever. The main couple got together, characters died, their lives were endangered: I didn't care through any of it.