The book provides a detailed study of the Biblioteca Apostolica Vaticana and its interior decoration which today still remains inaccessible to the ordinary visit. Placing the history of the Vatican Library in the larger context of how erudition was administered and organized within the Early Modern Roman Curia, the book will also take into consideration how the Vaticana was used in contrast to other newly founded libraries.

This book presents a critical edition of a collection of liturgical manuscripts that the Augustinian friar Onofrio Panvinio (1530-1568) assembled in the 1560s for the Cardinal Alessandro Farnese as well as for Hans Jakob Fugger in Augsburg. Onofrio Panvinio is primarily known for his antiquarian studies about ancient Rome and for his edition of Bartolomeo Platina's Lives of the Popes. His preoccupation with the Roman rite, however, remains until today largely unnoticed by modern scholarship. This edition of Panvinio's Vetusti aliquot rituales libri highlights his interests in the development of Roman liturgy during the last sessions of the Council of Trent (1545-1563) by presenting the various documentary as well as cultural layers of Panvinio's collection of Roman ritual manuscripts.

Guglielmo Sirleto has generally been acknowledged as a crucial contributor to defending the papacy’s claims over St Peter’s primacy, including the apostle’s legendary arrival to Rome before his martyrdom. Sirleto established himself as a pivotal prelate, who assisted Pope Paul IV in rearranging the ceremonial apparatus for the solemn celebrations of the Cathedra Petri (St Peter’s Throne). Scholars, however, were unable to properly examine his De praestantia basilicae Vaticanae, because the manuscripts of this discourse were never completely identified. The edition of this treatise will therefore primarily provide a reconstruction of Sirleto’s working methods in readjusting the ceremonial solemnities prescribed for the feast day of the Cathedra Petri according to Curial Ceremony. The second discourse concerns, on the other hand, a description of the basilica of Santa Maria Maggiore on the Esquiline Hill, which Sirleto composed for the Cardinal Bishop of Milan, Carlo Borromeo. In contrast to the edition of the first discourse in this volume, the Trattato sopra la chiesa di Santa Maria Maggiore is presented according to the correspondence between Borromeo and Sirleto.