That was entertaining though what I really like is a bit more depth to my reading. It's the sort of book I would read if I had a long commute and wanted to relax with nothing much on my mind.
Rankin serves up genre candy - a mix of sci-fi, fantasy and detective novel in an exotic but nevertheless familiar historical setting. He gives us a long and complicated plot which has quite a bit of a 'plot for the sake of plot' feel to it. Most of the amusement lies in the cleverness of his style and the level of detail in the worldbuilding - especially the integration of Victorian London with the fantasy elements.
I haven't read the first two books in the series. I liked this well enough that I might pick them up if I saw them, especially as most people in the know seem to feel they were better.