Commissario Brunetti finds that a Venetian library of rare books has suffered thefts. Some one has been slicing out pages of maps and illustrations from each half-century old book of travels. These are saleable separately and the main suspect is an American man. Do we value a book BY ITS COVER or as an investment?

The usual corruption seethes under the laguna waters. A massive cruise ship may be damaging the ancient buildings, but eight separate committees are looking into the tourist trade and must agree on any decision. GPS systems have been ordered for the police launch drivers - who don't want them - but have failed to arrive. Brunetti and his friend and co-worker Vianello sip white wine and munch light lunch as they discuss the haughty patroness of the library, who donated some of the damaged books. Everyone in Venice knows or is connected to everyone else, and gossip never gets forgotten. We learn that in Naples the library's own director, now in prison, had stolen copiously from the collection, altering the catalogue to hide his activities.

As with the rest of this series Brunetti does a great deal of walking, talking and contemplating rather than chasing robbers, so the appeal of this marvellous story is more for a sense of location than as a police procedural. Spring in Venice is scented with lilac, wisteria and lily of the valley; women sit at canal side cafe tables with their faces tilted up to the sun. Then a man believed to be a witness to the latest rare book thefts is found dead. Was he a mere onlooker, or a participant?

Donna Leon, the German author of this splendid series, now comes across as feeling crushed by the weighty, unstoppable momentum of Italian corruption. The casino here, she says, is the only one in the world which loses money. Her protagonist's formidable wealthy father-in-law is now moving his money to northern Europe and America. Although the Brunetti books do not deal with mobsters, just individuals, the underlying atmosphere of distrust of the law, of favours given and received, or money spent to secure a desired illegal result, is all-pervasive in her view of society.

BY ITS COVER looks simultaneously at the advance of the computer age and the heritage preserved in ancient manuscripts, pitting a weary hero against the infinitely ingenious criminal mind.