The series of beautiful sacramentaries made at Saint-Amand in the later ninth century offer us unique insight into an early medieval scriptorium at work. These manuscripts contain principally the prayer texts for the celebration of the Mass, a ceremony which stood at the centre of monastic life in this period. They display how this largely neglected genre discloses creativity and initiative on the part of the monks of Saint-Amand, who re-organised and re-composed this especially versatile literature. They made their books uniquely comprehensive and full of insight into how the mass liturgy was re-made at a critical period in its development. This innovative study makes these sources accessible for the first time. In-depth study of script, decoration, and content enables a new appreciation of the context in which the deluxe Saint-Amand manuscripts were produced. It foregrounds ecclesiastical patronage, the political and intellectual dynamics at the waning of Carolingian power, and the intensive collaboration of scribes, artists, and liturgical composers, as well as the unique ways liturgical manuscripts can inform our understanding of medieval life and thought.