A book like a fine steak....
That is to say, only medium well done. The cover blurbs of the copy I have make much of how 'horrifying' and 'brilliant' this book is, going so far as to compare it to Umberto Eco. I find it to be closer to the work of, say, Susan Kay.
Don't get me wrong, this book is entertaining. The concept of the scent-master is (as far as I know) quite original, and the theme is carried out consistently throughout the book. The author has a sharp eye for detail and is not afraid to stray from his plot for an interesting digression, which is always nice to see (myself, I would that he had more discretion in deciding what subjects qualified as 'interesting' but that is a matter of taste.)
However, the characterization of the mass murder as an amoral, asocial creature with delusions of grandeur is frankly overdone. It belongs in a Johnny the Homicidal Maniac comic. Worse, the author can never quite seem to decide how much irony he wants to lay on, sometimes seeming embarrassingly earnest, other times plunging his story into ridiculousness with a wink (Ok, we get it! Everyone who interacts with your main character is going to come to a bad end! How clever.)
As for the supposedly shocking and horrifying nature of this book, a heap of corpses does not true horror make. By refusing to allow any empathy for any of his doomed characters, the author may be trying to force us to take the point of view of his sociopathic protagonist, but in reality, he dries up the source of most of the potential emotional impact of the final chapters. The climax and finale are rushed, abrupt, and present a barely-surmountable temptation to skip ahead to the last page.
The overall impression I was left with was that the author studied so hard to be unsentimental that he fell over the edge into reverse sentimentality, a sort of simpering affection for nasty occurrences not coupled with any real insight.
You don't have to take my word for it....
Moral of the story? Failing to follow through on your aspirations, kiddies, is as bad as not having any aspirations at all. And you can be an international literary darling and still embarrass yourself and your readers.