I have reread Rivers Of London and Moon Over Soho. I thought the first was good anyway, but Moon Over Soho grew on me with a second reading. It is hard to believe that they aren't already being turned into TV series. I think on the whole they would be best served by (a) being done by ITV rather than the BBC and (b) being done by people who usually do detective series rather than fantasy.
Meanwhile, I see that the tube is the theme for volume 3 http://www.amazon.co.uk/Whispers-Under-Ground-Ben-Aaronovitch/dp/0575097647