Like most literary policemen these days, Rebus has a bit of an attitude problem (which has affected his promotion prospects), but most people like him because he has the guts to speak the sort of "truth to power" that people only dream of saying in real life.
In this book, we see a Russian poet and exile-cum-emigre seemingly killed in the street in the city center, after a night on the tiles (and the local Chinese restaurant, we later discover). Rebus, and his sidekick D.S. Siobhan Clark, investigate the circumstances of his death. Was it a mugging gone wrong, or something more serious?
The entirety of the book is spent trying to discover whether or not the character was killed in a mugging. Rankin uses what happened to Alexander Litvenenko in London as a tool to keep you guessing as long as possible (for those of you that don't know, he was a real life Russian emigre who was murdered by the KGB on British soil). The attempt at balance works for a while, but anyone who has read more than a few murder mysteries will know who committed about 2/3 of the crimes after you've read about 70% of the book.
The book is probably the most linear thriller that I've read by Rankin in years. It has a clearly defined beginning, middle and end, and has fewer asides about Scotland and the Scottish than I've seen in ages. This makes the central story flow better, but if you like the asides, you might not enjoy it as much as you enjoy some other books that Rankin has written recently.
Personally I don't think that anyone's going to completely satisfied at the balance between story and aside in a Rankin novel (it is a matter of personal taste after all), but this book, I believe, continues the improvement in the series that we have seen over the last few books and is much better than The Falls and Resurrection Men.