This one wasn't going to get reviewed. As soon as I'd finished it I started in on the next one. And by the time I'd got to the end of that I couldn't even remember the plot. Well, a week later I still couldn't, so I looked.
And that's when it hit me: although there is plot that isn't why I read them. They're cozies. The mystery itself isn't the point. I read them because I like Peter's snarky voice, and his relationship with his immediate and extended family; his alternate family at the Folly: both the unusual denizens of the house, but also his magical and nonmagical police associates; plus, too, there's the snug domesticity with his girlfriend and then her whole extended family. I like all the scientific questions that Peter asks about magic, and the experiments he comes up with as well as the tools, the sheer geekiness of him. I like how we're reminded that policework is all about evidence and grinding routine, even as there's always an opportunity for Peter to jump in with something brave and disastrously dangerous. And like everyone else, I appreciate seeing some of the millions of non-white and non-wealthy residents of London. And then too, there's rather a lot about food.
Really the only way it doesn't fit the archetype of Cozy in my head is that the lead isn't a woman, which isn't an assumption I was aware of before now.