But this is Tabucchi so the plot, while not irrelevant, is not all that is going on. Firstly, there is the humour. Tabucchi has a wicked, dry sense of humour which pops up unexpectedly throughout the book. Secondly, the book is full of asides, from Firmino's failed exploration of the modern Portuguese novel to the not unsympathetic portrait of the gypsies in the first chapter. Thirdly, Tabucchi, while definitely not writing a political novel, takes a definitely sympathetic view towards the downtrodden and oppressed but does it in a compassionate, a literary way rather than a polemical way. Fourthly, while this novel is nominally a mystery, Tabucchi is not concerned with who killed whom. We find out about half way through the book who was responsible for Damasceno Monteiro's death and, while Firmino and Loton try to bring the criminals to justice, it is apparent that they are not going to be able to do so. The point that Tabucchi is making is that life does not have a happy, tidy conclusion like mystery novels, where the detective gets the bad guy, but rather that life is untidy and messy.
Of course, all of this is all very well but it does not really explain why Tabucchi is such a great writer. The issue of personal responsibility is key to Tabucchi's work but Tabucchi does not drive the point home but rather skillfully brings out in a subtle and almost ambivalent manner, so that you think you are reading a mystery novel but you are not. You are reading the literary work of a major writer who is fully in control of his medium.