The calculated climb of the medieval gentry

The Paston letters sometimes seem too good to be true. Only in a historical romance could the Duke of Norfolk lay armed siege to a gentry family's recently built castle at exactly the time that a daughter elopes with their estate manager, son of a shopkeeper - which all coincides with the collapse of the political world in Warwick's coup against Edward IV. To repeat this trick in a three-generation epic for other crises of the so-called Wars of the Roses stretches credibility even further: Lord Moleyns's forcible occupation of the Paston manor of Gresham during the first breakdown of Henry VI's Government in about 1450; and the battle over Sir John Fastolf's will as civil war broke out in 1459-61. Yet such are the dramas contained in the most important collection of letters to survive from medieval England. Their story is the establishment of a new gentry family in East Anglia via legal success and investment in land, a process made traumatic by recurrent political collapse and usurpation between the 1440s and 1480s.

In Blood and Roses , Helen Castor works the letters into a narrative, retaining them at the book's heart by quoting liberally from them in judiciously modernised prose, which nevertheless preserves its 15th-century flavour. She deftly places them in context, taking account of the latest writing on East Anglian aristocratic society and late-medieval English politics. The verve and skill of this account will attract the growing general audience for history, but its academic credentials equally mean that students will learn a great deal about 15th-century society and politics.

A particular quality of the letters is the way they open up individual minds and perceptions. Castor is good at defining the problems the Pastons faced and the choices they made. Moreover, because the writers speak to us directly, it is possible to see how their characters influenced the course of events: Judge William's ruthlessness in investing his legal fortune; his son's mismanagement of Fastolf's legacy through mistrust of all around him and his inflexible refusal to compromise; his wife Margaret's strong-minded persistence in driving business on; and the complementary partnership of their sons - John II debonair and courtly, John III business minded but witty - which finally established the family at the top of local society, and is the highlight of the book.

Seeing the story largely from the Pastons' point of view risks persuading us they were representative of late-medieval gentry families, which has led to easy stereotypes of an unruly aristocracy fomenting violent times. Yet Castor's academic work has shown that the Pastons were neither innocent nor typical, rising rapidly through sometimes dubious methods in abnormal times.

Yet the Paston story can illuminate the late-medieval polity: Castor smuggles into her narrative a neo-constitutionalist reading of English politics that does not diminish aristocratic competition for power, position and profit, but places it in the context of royal government.

Political breakdown removed the protection of law and royal lordship, allowing the powerful and unscrupulous free rein to exploit neighbours and inferiors, and making peaceful resolution of disputes impossible. It was therefore no coincidence that the Paston crises occurred at moments of national political collapse.

Castor both instructs and entertains, allowing the irresistible charm of the letters' voices to speak clearly through her well-crafted text.

Benjamin Thompson is lecturer in medieval history, Oxford University.