By It's Cover (Commissario Guido Brunetti Series, Book #23) by Leon, Donna - 2014

In the pages of Donna Leon's internationally bestselling Commissario Guido Brunetti mysteries, the conversations of the Brunetti family have often turned to topics of art and literature, but books are at the heart of this novel like never before. One afternoon, Brunetti gets a frantic call from the director of a prestigious Venetian library. Someone has stolen pages out of several rare books. The obvious culprit seems to be the man who requested the volumes, a visiting American professor. But it soon becomes clear that the professor is not who he said he was. As the investigation proceeds, the suspects multiply. And when a seemingly harmless character turns up brutally murdered, Brunetti must question his expectations about what makes a man innocent or guilty.