This was great! The best JL I've read in a long time and easily her best mystery to date. I haven't had a lot of luck with a lot of Josh's books lately. Either they just haven't interested me at all (Jefferson Blythe, Wizard's Moon), or I had just as many issues with them as I things I liked about them (Fair Play, Everything I Know, Baby It's Cold). I'm glad to say this one breaks that streak. This feels more like one of her earlier works, with strong writing, strong characters and a complex mystery.
It's not as focused on the romance, though it is there. And yeah, it's practically instalove, despite the initial dislike both MCs have for each other, but as the focus wasn't really on the romance it worked for me. Jason is an interesting character. He's out of his depth, and recovering from a recent shooting where he was injured. He's meant to be a watchdog for Sam Kennedy, who is on the bureau's crap list at present and not happy to be partnered again. I did wish at points that we had some of Sam's POV as I would have liked to know what was going through his head in regards to Jason and his changing attitude toward him. While the ending isn't HEA or even HFN, there's potential for more between these two.
There were several potential suspects here and just enough info given to make each one a plausible whodunit. JL doesn't let her characters be stupid and ignore obvious connections or potential leads no matter how far fetched, and she creates characters who can be living and breathing people, with their own motivations. It certainly lends to the mystery for the reader as well. I usually have the suspect pegged by the halfway mark if not sooner, which makes for annoying reading when the characters are just not getting it. I didn't have that experience here, and even(show spoiler)
The writing is hauntingly atmospheric at times, particularly during the scenes in Rexwood. Jason and Sam might not like each other at first, but they're professionals and they deal with the situation as professionals, not like whining brats in a school yard as other authors might do. There were a few times when the writing threw me out of the scene though, particularly the end of the first sex scene. What were all those surf and turf metaphors for? Jason's from LA, he likes to surf. The murders center around mermaid trinkets. It still felt a little forced and overly done. There were a couple of other little moments like that that keep this from being a full five stars.