'Whispers Underground' is the third book in what appears to be an ongoing series (wonderfully, author Ben Aaronovitch has said that he plans to keep going until he can afford a yacht) about Peter Grant, official apprentice to the last officially-sanctioned wizard in Britain. Although, as one of the threads running through the novel shows, the last officially-sanctioned wizard is very much not the same thing as the last wizard. This thread, which was frustrating to me at the end of 'Moon Over Soho', has been developed quite well here (there's a great gag where the mysterious rogue wizard leaves a psychic trap in Elvish that Tolkien fans translate as, "If you can read this, not only are you dead but you're also a huge nerd.") I don't even mind the fact that it's still dangling by the end of this book, now that I'm used to the idea.
One of the other minor complaints I had about the last book turns out to have been very well-thought out for the long haul as well. Not to unduly spoil 'Moon Over Soho', but Peter has a very different attitude when it comes to "monsters" than his superior. In the last book, this kind of came to nothing, because fate sort of took its own course, but that only heightened the tension of this novel. When Peter finds an entire underground civilization beneath London, one with a tangled and extra-legal relationship with the seedier denizens of the city, the question of what exactly is going to happen to them once the larger world finds out becomes all the more razor-edged due to the events of 'Moon Over Soho'. By showing that the world isn't always cute and cuddly towards the inhuman, Aaronovitch gives us one more reason to find the story gripping.
And it is. What starts as an ordinary murder turns into an exploration of the magical underworld, literal and figurative, of London. It's exciting stuff, and Aaronovitch makes it (as always) witty and exciting and funny and scary and nerve-wracking and just generally excellent. Oh, and recurring character Lesley May gets a hugely expanded role for this one, which is just plain awesome because she deserves it.
In case I'm not being clear here, this one's a good buy too.