I got this out of the library at the same time as Rivers of London, on the off-chance that I'd like the first one enough to read the second one without having to hunt around for it (or, gasp, pay for it). Well, I did enjoy the first one, and this sequel was fun and inventive too - but slackly structured, not very exciting and frankly rather confusing. I might wait to read the rest.
(My excuse for the unprofessionally borrowed-from-Amazon cover is that my usual Google Books source failed to offer a hi-res version. If you look really carefully, you might be able to see "Convent Garden" in the picture and wonder, like me, whether this is a deliberate mistake or a real one they're passing off as deliberate...)