Meh. Definitely not the strongest in the series so far. Ryan had a Rear Window theme going on in the plot, and I'm not a fan of the trope, although I give her credit for using it as an effective device for bringing society's view of seniors, and how easily they're dismissed, into the book's storyline.
The mystery itself was obfuscated by both the question of whether or not a crime took place at all, and the lack of any clear motive until very nearly the end of the book. By the time it's revealed that a crime did take place, it was pretty clear who had to have done it.
While I generally love the setting (I find the whole repurposing thing interesting), and I like the characters, I found Rose (the witness the maybe crime), in particular, a bit trying. She was just a little too exaggerated. There's a weird romance vibe going on in the series too; it's not quite a love triangle but the potential is obvious. Meanwhile nothing but internal musing has been going on for 4 books and I'm tired of hearing about it. One party of the triangle, Nick, seems to have zero chemistry with the MC and was a total ass in this book. Total. ass.
I'll read the next one on the strength of the author's other books, and how much I usually enjoy them. Hopefully the mystery, at least, will be a better one.