What a bore. As usual with these sorts of writers when they no longer have a plot in them they turn to political-social issues. In this case the relationship between pollution, glass-making and politics in Venice.
It isn't that I totally don't want to read about these things, but if I do, I will not choose to do so via the conduit of a murder-mystery.
So, no plot to speak of, and on top of that, dreadfully proofread. The book is laced with words hyp-enated for no rea-son whatsoever. I'm guessing something was taken out or added and nobody bothered to check the impact on the type-setting.