Death at La Fenice #1 by Donna Leon

There is little violent crime in Venice, a serenely beautiful floating city of mystery and magic, history and decay. But the evil that does occasionally rear its head is the jurisdiction of Guido Brunetti, the suave, urbane vice-commissario of police and a genius at detection. Now all of his admirable abilities must come  into play in the deadly affair of Maestro Helmut Wellauer, a world-renowned conductor who died painfully from cyanide poisoning during an intermission at La Fenice.

But as the investigation unfolds, a chilling picture slowly begins to take shape—a detailed portrait of revenge painted with vivid strokes of hatred and shocking depravity. And the dilemma for Guido Brunetti will not be finding a murder suspect, but rather narrowing the choices down to one. . . .