After nine books, Donna Leon can be excused for trying too hard to come up with something new for book ten.

The main characters are the charm of this series: initially, Inspector Brunetti, his wife, Paola, their family, and the city of Venice. Book three adds Signorina Elettra Zorzi, an impossibly sophisticated, stylish, perceptive, attractive, computer whiz, to this group. Elletra has left a well-paying, prestigious job at a bank to work for Brunetti's boss. She jiggles the police station's budget to provide magnificent fresh flowers for her office and serves as a sort of deus ex machina, providing the information Brunetti relies upon to solve mysteries and punish wrongdoers. Elletra accomplishes these miracles using incredible hacking skills; a wide network of friends and other relationships; and a sophisticated understanding of human nature.

Surrounded by a world and people who are plausible, Elletra is utterly unbelievable. She can find any information and is owed favors from people in all sort of government agencies. Elletra's magic was tolerable for a few books, but subsequent books reveal nothing to make Elletra any more believable or give her any depth.

None of the characters in the series develop -- they become increasingly two-dimensional but remain likeable. Unfortunately, Elletra is more of a problem. She remains the only character who routinely performs miracles and plays a large part in solving nearly every mystery.

She plays such a large role that the series became rather boring: Murder; Elletra discovers most of the facts; Brunetti eventually figures out who the killer is. I continued to read the books pretty much as one continues to read a boring comic strip -- hoping to be surprised but tolerant of the monotony.

Donna Leon, perhaps striving for something less monotonous: making the action of the book revolve around the actions of a main character. If done well, the chosen character can emerge more rounded and nuanced than before.

Sadly Leon does not do it well. The two times Leon tried this, her characters do things so utterly foreign to them that the plots are ridiculous. The first time, in book 8, Brunetti's spouse, a university lecturer, mother of two teenagers, and offspring of Venetian royalty, starts heaving rocks through the window of a travel agent to interfere with the agency's sex tourism business. Huh?

In this book, Signorina Elletra decides, against advice, to go undercover to find information about the murder of two clam fishermen. She discovers no useful information whatsoever. Instead the infallible, all-knowing Elletra falls in love with a handsome young man, the man who tipped off the killer about who turned the killer into the tax authorities, triggering the murders. The young man lies about his background -- he does not reveal to Elletra that he worked for the tax departmen; and introduces her to his uncle, the killer of the fishermen. Elletra is uncomfortable around the uncle, but though nearly omniscient through seven books, gets onto a boat with him. The uncle, knowing Elletra works for the police, tries to kills her. She ends up responsible for the death of a police pilot (near retirement) who ill-advisedly tries to rescue her during a terrible storm. The police boat is destroyed. And her actions kill the young man she is in love with.

The book wraps up, not with laying the blame for these disasters at Elletra's feet, but with everyone feeling terribly sorry for poor, vulnerable Elletra.

It's ludicrous.

Leon may be excused for trying something new and even for concocting ridiculous plots -- after all, this is book ten in the series -- but that doesn't a reader needs to uncritically accept the results.