The study of cardinals has flourished since it was pioneered by David Chambers in the 1960s, and Byatt's work breaks more new ground. Neither a conventional biography, nor a discussion of artistic patronage, both popular themes in the field, her text concentrates on the court of cardinal Niccolò Ridolfi in the light of contemporary treatises on household management. This was a new genre, one which underlined the importance attached to display as an indicator of status; and it was an issue of particular significance to Ridolfi who was not born noble but had acquired the status of prince with his red hat and for whom his court was one of the most public signs of his new rank.

The book is divided into three sections, the first of which deals with Ridolfi's Florentine background and early career. His parents, Piero Ridolfi and Contessina de’ Medici, daughter of Lorenzo the Magnificent, had married in 1493, though the political advantages anticipated by the match evaporated when the Medici were banished eighteen months later; by the time the future cardinal was born in 1501, his Ridolfi grandfather was also dead, executed for loyalty to the exiled family. But his fortunes revived in dramatic fashion in 1513 when his cousin Giovanni de’ Medici was elected Leo X. Ridolfi was made a cardinal in 1517, one of many papal relations to receive a red hat, and his career continued to prosper under Clement VII. Thanks to the Medici popes, he accumulated benefices and other favors that brought him an income of 15,000–20,000 gold ducats that, although it did not put him among the richest members of the College, made him wealthy enough to finance an appropriately lavish lifestyle.

Part 2 deals with Ridolfi's court at his palace at Sant'Apollinare in Rome. Using the analogy of above- and below-stairs staff, Byatt makes the distinction, often ignored or misunderstood, between courtiers and servants, giving lucid definitions of the terms involved, respectively familiare and famiglio. Her discussion of the court is based on an analysis of three treatises: Cola Cerretano da Benevento's Del governo della corte d'un Signore in Roma (1543), which, as she convincingly shows, was not written by Francesco Priscianese but published by him; Mauro Salvidio's Trattato . . . [per] regger’ et governare la corte di un magnanimo, & generoso prelato (1544); and Domenico Romoli's La singolare dottrina (1560), a much longer work concentrating on the role of the steward (scalco). Importantly, all three had close links with Ridolfi. Cola da Benevento was the cardinal's majordomo, appointed after his predecessor was dismissed for theft while Salvidio, who dedicated his treatise to Ridolfi, claimed long service in the household and Romoli appears in Ridolfi's ledgers in connection with spices and the wardrobe.

Using Cola da Benevento's description of the ideal household, Byatt outlines the roles of its senior members: the majordomo, gentlemen of the chamber (camerieri), and those involved with the cardinal's business affairs, such as his secretary and purser. She then turns to the provision of hospitality, an important duty of a cardinal, discussing the members of staff known as the “officials of the mouth” who included both gentlemen such as the steward and the carver, and servants, including the purchaser, cook, and credenziere. A second chapter covers food and wine as well as laundry, lighting, and other practicalities of life in the palace. She also discusses travel and ceremony, both significant aspects of his expenses that formed a key element in his display of prestige; and she includes a useful section on the cardinal's stables, an expense that is invariably overlooked.

Part 3 deals with Ridolfi's later career as well as his patronage of learning and of his particular interest: medicine. By the mid 1530s, he had become disillusioned with the princely ambitions of the Medici and joined the growing number of exiles (fuorusciti) from duke Alessandro's unpopular regime. Despite the enmity of Cosimo I, or perhaps to make up for it, he established cordial relations with Paul III, outlined in a chapter on Ridolfi's support for Church reform that led to his appointment as bishop of Vicenza and his ceremonial entry into the city (1543). The last part comes as a bit of a shock after all the domestic and ceremonial detail. On January 31, 1550, during the conclave following the death of Paul III, Ridolfi died in very suspicious circumstances. He had been among the candidates for election, and the suddenness of his death persuaded his doctors to perform an autopsy that indicated that the cardinal had been poisoned. Several years later, Giovan Francesco Lottini, an agent of Cosimo I, stood trial on charges including this murder, but the case was dismissed (both the autopsy and an account of the trial are published as an appendix to the book).

Byatt's book considerably widens our knowledge of a cardinal's court and, in particular, introduces the reader to three important treatises on household management, which increase our understanding of what was expected of a cardinal in the years immediately before the Counter Reformation. It would have been interesting to learn more about the men—gentlemen and servants—who belonged to the household, how and why they were appointed, and how Ridolfi exploited his family connections, but that is perhaps outside the scope of this book. What we have is a fascinating account of domestic life at a cardinal's palace, showing not only how Ridolfi himself lived but the members of his household too, what they all ate and drank, how they kept warm, and so on. It is a unique insight into life of the period and an important contribution to the literature on Renaissance cardinals.