I was immediately hooked on this story. I didn't really clue in until near the end that it was a little mermaid retelling, but that's good, I like when they are not so obvious.
I've always found writing from several character perspectives adds a fullness to the story that wouldn't be achieved otherwise, and Christo did this well with Lira and Elian. I found myself excited to learn the other character's thoughts on certain events and with this writing style that excitement is sated perfectly.
I think the immediate darkness of the story really attracted my attention. Characters that have darkness in them while still maintaining the ability to do good seem much more real and hey, I just enjoy dark things. It was a bit predictable what would ultimately happen by the end, but I didn't know how we would get there and it didn't take away any of the enjoyment.