The mermaid mythos was pretty cool, but I'm more than a little disappointed that feelings got in the way of the murder. ... Seriously though. It was much more compelling before the really badly constructed romance ruined everything. 
 Calder was pretty gross when it came to how he tried to "seduce" Lily. And I get it in the sense that he's trying to get close to her to murder her dad (for plot reasons!), but it got played off as sort of okay and romantic in the end and just. No. No no no. Gross. Calder actually uses the phrase, "And besides you kind of owe me" completely seriously. NO. GROSS. STOP. 
 Hence why it would've been better if it was just all murder no feelings. Because otherwise the narrative tries to excuse the grossness and again. No. It was also disappointing because Lily was definitely not having any of that nonsense at first, which was great, but literally all Calder had to do was buy a book of poetry and she was suddenly completely into him? I just don't get it. 
 There was a lot of cool mythos and themes that could've been explored and it all just sort of got dumped aside for the sake of a terribly flimsy romance. (view spoiler)[And there was even a whole bit of "she's not really your sister so it's not really incest!" bit again. Can we just STOP with that please? (hide spoiler)] And the big twist involving the debt owed was pretty lackluster. 
 1.5 stars. I'd probably skip this one.