Whispers Under Ground by Ben Aaronovitch

In this book PC Grant goes underground when a US Senator's son is found stabbed in the back in the Baker Street tube station. Aaronovitch does a great job developing his characters--his stories have real consequences, and these consequences play out in real ways. The landscape of the stories is also rich: you really feel like you're in London. There are a number of Lord of the Rings references, which I thoroughly enjoyed. The faceless man (the big bad introduced in the last book) is still hovering, but I think that adds to the series's appeal. If you're a fan of Harry Dresden, these books should appeal to you.