This is book 3 of the "Rivers of London" series.

This note contains spoilers for the book.

Death of the son of an American senator, in a London tube tunner, with a broken strange stoneware magical artifact. An FBI agent is assigned to observe, and a mysterious Taiwanese practitioner turns up. River Fleet seems to be the river of this book.

I have determined from querying my friends what the joke about the model of Peter Grant's car (or cars) is. They're mostly called a "Ford Asbo" in the books. An "ASBO" is an anti-social behavior order, a judicial thing used to attempt to create leverage on habitual minor offenders. So why is the car named that? I didn't quite connect all the dots; the car is a Ford Focus ST, which is a fairly hot hatch-back. Apparently Jeremy Clarkson on Car Talk gave it the nickname "Asbo" because it encouraged driving that might get you an ASBO.