The letters of Castiglione were written following the immediate contingencies of daily life, without implicating any strenuous formal or expressive research, and outside the bounds of any extrinsic aesthetic preoccupation. Nonetheless, the style is never flat or neutral, because the author is always seeking persuasiveness and the power of illumination, aiming to establish with the interlocutors a lively relationship and exchange. The language of Castiglione in his private correspondence tended systematically towards the concinnitas (= elegance) theorized by Cicero: for a natural grace that, avoiding straying too far from common uses, should reflect the personality of the author.

Sometimes Castiglione wrote very long letters and on other occasions short and simple notes. But his prose was always, in every case, permeable and elastic, so as to transmit the richness and complexity of every situation referred. Facing a natural countryside, a city, a person or an animal, his descriptions were never generic or abstract. He always tended towards the most economical and efficient expressive form. Sometimes circumstance or convenience obliged him to use a more controlled and less effusive style; instead, on other occasions, his curiosity and his skill as an analytical observer raised the level of his letters, so that his private letters would become an opportunity for transmitting to the recipient a page of great news, of high life or gallantry. The lights and splendours of court life were described with passion and linguistic precision, without ever, though, hiding the dark areas, the preoccupations and jealousies that permeated that same world. Castiglione was always precise, concrete and never held back, if possible, from talking about the most grotesque, scandalous or violent details: the murder of Giovanni Andrea Bravo from Verona by Francesco Maria Della Rovere, the autopsy carried out on the body of Cardinal Luigi de’ Rossi, the crazy bets and the local brawls typical of the Rome of the early 16^th Century.

Raffaello, Leone X between cardinals Giulio de’ Medici and Luigi de’ Rossi (right), Florence, Galleria degli Uffizi