The Ruby in her Navel by Barry Unsworth

Meet Thurstan, Purveyor of Pleasures and Shows in the Diwan al-tahqiq al-ma'mur of King Roger of Sicily: a blond-haired Norman who cares about clothes and girls, enjoys singing and getting laid. He is the narrator of Barry Unsworth's 15th novel, born to knighthood but compelled by circumstance to the altogether sissier occupation of royal talent scout. The year is 1149. Sicily is threatened by the rulers of the Western and Eastern empires, "the two most powerful men in the world", and Christians and Muslims are vying for King Roger's favour. Thurstan works for a highly placed Muslim whose downfall the Christians are plotting and, despite his boss's best efforts to instruct him, displays a total lack of guile as he navigates the political and religious intrigues of medieval Europe.

On a mission to purchase birds for the king's falcons, he comes across a dancing troupe and takes them back to Palermo to perform at court. One of the dancers is Nesrin, the possessor of the navel in the novel's title, and the horny young Norman is immediately entranced. But there are other temptations, too, not least the suspiciously coincidental reunion with a childhood sweetheart, the lady Alicia, who takes him to glamorous parties and promises riches, love and the prospect of purity.

Unsworth is no stranger to historical fiction, and among his previous subjects are the decline of the Ottoman Empire and the Atlantic slave trade. He is clearly an avid researcher with a taste for the colourful backdrops - architectural and cultural - of the past, and in this case the tensions of Europe at the time of the crusades are given an uncomfortable relevance by current Western misadventures in the Middle East.

The writer of a first-person narrative faces many challenges, which multiply if the setting is historical. One is the need to convey information to the reader which the narrator knows. Another is the narrator's choice of diction - should the novelist be consciously archaic, or write in a manner more accessible to modern readers?

Unsworth adopts a curious register, sometimes "medieval" in its word order but essentially modern. This can lead to occasional moments of jarring dialogue: Thurstan dreams of "having Alicia to himself for a while"; he asks her when they will have "time for ourselves" and she promises constancy until they "can be together". Later, when she doesn't show for a date, her representative assures Thurstan that "this changes nothing". The political complexities of medieval Europe are explained by the characters, which leads to conversations like the one in which the King's PR guru remarks that "Corfu has fallen to the Byzantines, as all of us know to our cost."

Unsworth does not, perhaps, succeed in taking us vividly and with realism into the past, as Mary Renault's novels of classical civilisation do - but how much does that matter? To some it will matter a great deal. Others will find an entertaining story of sexual temptation, forbidden love, crazy monks and treacherous Christians: a riotous period soap opera.