Of the two 'Kurt Wallander' novels I have read, 'The Dogs of Riga' is the weaker: 'Faceless Killers' has a more compelling plot, and a more interesting narrative. However, 'The Dogs of Riga' is still a very good book. The ending is slightly cluttered, with Mankell pushing credibility a little, but the novel as a whole is an excellent portrait of a determined Swedish Police detective who happens to be a little unlucky and a little unhealthy.
'The Dogs of Riga' is basically a Police Procedural detective novel and a no-details-ignored, everything-included study of a middle-aged man going through a variety of problems, whether they be medical, personal, or career-related. We may not aspire to be like Wallander in all respects, but the character earns the respect, admiration, and - at times - symphathy of the reader. Mankell weaves the most mundane details of Wallander's life and police investigations into a narrative which is always compelling. And he is astute not only with regard to character: there is a superb sense of geographical place, time, and politics in these novels. And this sense is nuanced, and not in any way simplistic. If anything, Mankell paints the world in too realistic a way: it is so plausible and real that reading about certain aspects of it can be depressing.
Recommended, although 'Faceless Killers' is the first novel, in terms of Wallander's chronology. After reading 'Faceless Killers' and 'The Dogs of Riga', read 'Sidetracked' and 'The Fifth Woman', in that order.