If there's a writer for whom the law of diminishing returns has been revoked, it's Donna Leon.

The doyenne of Italian crime fiction, whose stamina in returning time and again to her Venetian beat is matched only by her curiosity, she has proved herself, in the space of 22 titles, not only an able detective novelist, but the author of something more substantial.

As we find ourselves once more in the company of Commissario Guido Brunetti, a gentlemanly, bookish policeman who never takes a short cut if it would impede his ruminations on life, it becomes clear that, with this character, his sparky family and colleagues, Leon has been weaving a literary equivalent of the Bayeux Tapestry: a scene-by-scene depiction of a world far from our own, yet, in its venality and superstitiousness, aspirations and idealism, decidedly familiar.

With a city such as Venice, crime offers probably the swiftest clues to its character. Of course, it has not harmed Leon's career that she has chosen one of the most theatrical locations on the planet as the backdrop to her series. For some, the pleasure of her work lies in its setting. No matter how grim the events portrayed, there is the balm of Venice's enchanting alleys and canals to distract one from the cruelty and greed that underpin much of life here, as everywhere. Others, such as myself, are less fascinated by Venice's beauty, though, than by Leon's insights into Italian culture, and the dark mysteries of its political bureaucracy and criminal overlords, forces that often overlap.

The focus of The Golden Egg, however, is narrow and local, Leon on this occasion not gunning for the big beasts. It might equally have been titled The Curate's Egg, so clearly does it display the range of virtues and sins among ordinary Venetians. As Brunetti faces the self-serving demands of his svelte superior, Vice-Questore Patta, whose cameo appearances are a pleasure as always, his wife learns that a deaf-mute who worked in their dry cleaner's shop has been found dead after taking an overdose of sleeping pills.

Increasingly disturbed as she realises how little anyone knew about this simple-minded man, Paola presses her husband to find out what happened. Expecting to uncover nothing suspicious, he stumbles instead upon a story that chills the blood. This, one of the most domestic and undramatic of Leon's tales, proves also to be one of her most harrowing.

At its core is the dead man's mother, a woman who lies as easily as she breathes. Around her is a community of working-class Venetians, for whom the state is the enemy, and who, when questioned by police, become as deaf and mute as the poor departed fellow himself.

As Brunetti pursues this case, Leon sits back and allows Venice to rise before us, evoking its personality and everyday habits with a relaxed eye. A city whose independent spirit sets it apart, its mood is mirrored in Brunetti and his wife who are not only deeply cynical about their secular leaders but fervently non-religious. Pondering the subtlety of language, a gift the deaf-mute never enjoyed, Brunetti asks his family: "'Do you think God is language?' [His son] Raffi was having none of this. He held up a forkful of cake. 'God is plum cake,' he said and took communion.'"

It is one of the joys of Leon's work that she can take readers into the sinister heart of Italy, and yet, in the person of Brunetti and his companions, convince us that not all is lost.

the golden egg

Donna Leon

Heinemann, £17.99