I'm ambivalent about this one. I've read all the books in this series, and am glad to read about the further adventures of Ellie and her colleagues in the MPD, especially Santiago, but I thought the plot was a little boring, formulaic, familiar, and predictable.
I'm really glad Watterson delved more into the personal relationship between Ellie and Santiago [although I thought his romantic feelings for her in the last book had a whiff of "that came out of nowhere"] and seems to slowly be developing something more between them. (Can you tell I don't care too much for Bryce? It's as Dr. Lukens told Ellie, maybe she and Bryce just aren't right for each other.]
The mystery, as I said earlier, was predictable. I had guessed the connection between Dr. Luken's patient Rachel and the killer fairly early on, and not too much later, guessed the "relationship" between Rachel and Lea. The only suspense for me was in wondering how the killer would be caught.
One thing I felt was "off" was this: even if the relationship between Ellie and Bryce is at a crossroads, wouldn't he have called her just to talk and in the course of it, found out was she injured in the line of duty? Some time has passed since Ellie was injured and the end of the book, but it didn't seem like Bryce knew about her injury, or even bothered to return to Wisconsin?! Given that money and job responsibilities are not a problem for him, why wouldn't he return? That seemed like a plot hole.
But the main issue I have with this book is the ending. It seemed pretty abrupt. It was such a weird way to end a novel, and it felt to me like there should have been another chapter, or at least a few more paragraphs added. And for those wondering, the end was only tangential to the main plot of the whole book! So double weird.