'An Icelandic novel of secret symbols, medieval witchcraft, and modern murder' - the subtitle of Last Rituals seems a desperate attempt by the publisher to leave nothing to the reader's imagination. Since the triumph of The Da Vinci Code in the thriller/mystery genre, publishers have scrambled for books that promise permutations of the esoteric-exotic-mystique combination so successfully deployed by Dan Brown.

Yrsa Sigurdardottir, an Icelandic writer of children's novels, has switched tracks to adult fiction with a thriller that revolves around demon worship. Predictably, it starts with the discovery of a corpse, its eyes gouged out and a strange symbol carved on the chest.

Harald Guntlieb, a German student attending graduate school in Iceland, is researching the country's history of witch-hunting for an academic paper when his strangled body is discovered by his history teacher, Gunnar Gestvik. The police arrest a drug dealer in whose company Harald was last seen. Harald's wealthy parents are unconvinced - the gruesome and eerie details of the murder belie a drug deal gone bad - and dispatch Mathew Reich, a family representative with 'investigative experience' to seek the real killer. Mathew, however, has language difficulties. Enter Thora Gudmundsdottir, a German-speaking native Icelandic lawyer.

As Thora diligently tracks down Harald's friends and colleagues she discovers the victim was a weird sort: the focus of his research was a 15th-century treatise on witchcraft called Malleus Mallificarum; he had sliced his tongue in two, and pierced it; was the founder of a black-magic society; independently wealthy courtesy of a kindly grandfather, yet estranged from his parents.

Thora's investigative forays are narrated entrancingly as our plucky heroine frequently spars with her partner, the meticulous Mathew. Her reflections on the life of a single parent, and interactions with a hormonally charged 16-year-old son, will no doubt appeal to female readers.

The even-paced narrative, however, is mostly devoid of any attempt to build atmosphere (something other contemporary Scandinavian writers employ with skill), or create any cliffhanging climaxes, as the heroine trudges through an increasingly arcane jungle of sorcery and magic symbols. As the mixed appeals of the rakish Harald become clearer, the sexual tension between the Nordic Thora and Germanic Mathew heightens, and at home Thora faces imminent chaos.

The book was originally written in Icelandic and translated into English - that may account for some of the loss in the narrative: the odd turn of phrase, the humour ('dark humour', the jacket cites) that often falls flat and the sometimes sketchy descriptions.

For a whodunit, it commits the cardinal sin of being too predictable: halfway through the novel the identity of the murderer becomes apparent.

Where the book works is in its skilful characterisation of the heroine, Thora Gudmundsdottir, and her travails as a mother, woman and professional. Thora peppers the narrative with humorous insights into the pronunciation of Icelandic language, the motoring habits of her countrymen and the consequences of having a small population as she trudges across the ice-laden landscape - tidbits that prevent the reader from forsaking the heroine even as the plot draws thin.

If you are interested in medieval Norse literature, or are curious about Iceland - an island country seldom in the international news - you might want to pick up this book. As a cracking mystery, however, it comes up short.