The only reason for the four stars instead of five is because it was predictable at times.
For instance, I knew in the opening precisely what actions Davies would take against the rotund Bavarian down to the conclusion of that encounter. It wasn't poorly written -- the whole book was well done in that regard -- it was just predictable.
Many times through the book I would jump ahead at the end of the scene, in my mind, because I thought I knew what was going to occur. And, for certain, it happened precisely the way I envisioned. The plot was engaging and entertaining, the characters lacking a little depth, but not horribly so. Still, I would have loved to have been able to sympathize with them a bit more, not just read about them. Dialogue excellent.
Overall, an intriguing read that you aren't likely to be disappointed in.