Queen Emma And The Vikings, by Harriet O'Brien

She was the wife of two kings - and the mother of four more

Emma is not one of our best known queens, but she richly deserves this illuminating biography. She married two English kings (Aethelred the Unready and Cnut), saw two of her sons (Harthacnut and Edward the Confessor) and two stepsons (Edmund Ironside and Harald Harefoot) win the English throne, made several comebacks from disgrace, and emerged as the only pre-Norman Conquest royal to have her bloodline continue after 1066. Duke William of Normandy, who grabbed the English throne from Harold Godwin, was her great-nephew.

Explaining how she achieved all this is no easy task, given the paucity and unreliability of contemporary records, the genealogical complexities of marriages and concubinages between Anglo-Saxons, Normans, Danes and Norwegians, and the constant ebb and flow of Norse invaders into England, punctuated by truce-making, truce-breaking and vengeful massacres. But Harriet O'Brien succeeds both in mapping the muddled decades between 1000 and 1066, and in constructing a plausible picture of Emma - or Aelfgifu, as her English subjects preferred to call her.

It is not a loveable person who emerges, but she clearly had true grit. Born around the late 980s, she was the daughter of Richard I, Duke of Normandy. Her marriage to the rather older Aethelred (in 1002) "may well have been formal, possibly slightly frosty", but she bore him two sons and after his death struck lucky. Cnut, the 20-year-old son of the Danish conqueror of England, Swein Forkbeard, chose to marry her when he succeeded to the throne.

The book she commissioned in 1042 to give her version of her life declares that "it is hard to credit how vast a magnitude of delight in one another arose in them both". The marriage may have been helped by the fact that Emma's mother was Danish and her father the grandson of the Viking Rollo, first Duke of Normandy.

Short of facts beyond the fascinating Encomium Emmae Reginae, O'Brien makes the best of things by plumping out her story with imaginative re-creations of significant scenes and lively social detail. She conveys the striking contemporary contrasts between extreme brutality and intense religiosity: lewd riddles and the noble nudity of Lady Godgifu (Godiva to you), stargazing and saint worship.

Christina Hardyment's 'Malory' is published by HarperCollins