The full text of the Gospels (the four accounts of Christ's life attributed to Matthew, Mark, Luke, and John, respectively), often accompanied by introductory matter such as the Prefaces of Saint Jerome, Eusebius' canon tables (with or without corresponding marginal numbers in the text indicating Eusebian sections or chapter numbers), and chapter lists (capitula). By the seventh century, what had been a practice of continuous reading from the Gospels during daily Church services (lectio continua), with specific passages prescribed only for major feasts, was replaced by the assignment of a specific passage (pericope) for each day. Gospel lists (capitularies), which listed pericopes by their incipits and explicits and were arranged to follow the liturgical year, were often included in Gospel books. Carpet pages, incipit pages, Chi-Rho pages, evangelist portraits or symbols, and other illustrations appeared in Gospel books from the seventh century on. There are a number of sumptuous early medieval Gospel books (many of them connected with important cults and patrons), as well as working versions used in the liturgy and Irish pocket Gospels. From the late eighth century, Gospel books were partially replaced in liturgical use by evangelaries, containing the Gospel readings for the year.
Michelle Brown, Understanding Illuminated Manuscripts (Malibu, CA: J. Paul Getty Museum in association with the British Library, c1994).