The book of hours is a Christian devotional book popular in the Middle Ages. It is the most common type of surviving medieval illuminated manuscript. Like every manuscript, each manuscript book of hours is unique in one way or another, but most contain a similar collection of texts, prayers and psalms, often with appropriate decorations, for Christian devotion. Illumination or decoration is minimal in many examples, often restricted to decorated capital letters at the start of psalms and other prayers, but books made for wealthy patrons may be extremely lavish, with full-page miniatures.
Books of hours were usually written in Latin (the Latin name for them is horae), although there are many entirely or partially written in vernacular European languages, especially Dutch. The English term primer is usually now reserved for those books written in English. Tens of thousands of books of hours have survived to the present day, in libraries and private collections throughout the world.
The typical book of hours is an abbreviated form of the breviary which contained the Divine Office recited in monasteries. It was developed for lay people who wished to incorporate elements of monasticism into their devotional life. Reciting the hours typically centered upon the reading of a number of psalms and other prayers. A typical book of hours contains:
A Calendar of Church feasts
An excerpt from each of the four gospels
The Little Office of the Blessed Virgin Mary
The fifteen Psalms of Degrees
The seven Penitential Psalms
A Litany of Saints
An Office for the Dead
The Hours of the Cross
Various other prayers
Most 15th-century books of hours have these basic contents. The Marian prayers Obsecro te ("I beseech thee") and O Intemerata ("O undefiled one") were frequently added, as were devotions for use at Mass, and meditations on the Passion of Christ, among other optional texts.