Difficult to rate. The writing is definitely worth a 4, but I settled on a 3 just for my own enjoyment level. Should be a 3.5, I guess.

It's an incredibly bold choice to reveal to us the outline of what was really happening, but also make it more than clear that there was never going to be any real justice in this situation, that Brunnetti may have managed to save the friend he made and clear the toxic waste out of one little area close to his home, but the toxic waste is still going to kill someone else, just in a different area. The book is about government corruption, and as such it's very realistic and very depressing. I respect having it end like that, but it isn't what most readers want out of a mystery and I hope that some of the other books in the series do have a more satisfying finale.

All that said, Jo Walton describes it as a book about integrity, and yeah, that's one way to look at it. As bleak as it is, there are a series of characters who choose to do the right thing, despite the danger.