Book of hours
A book of hours is a breviary containing prayers, Psalms, antiphons, and other materials to be recited at the canonical hours. These books were popular during the Middle Ages for common use among the nobility and the clergy. One of the most famous is the Très Riches Heures du duc de Berry.
Book Of Hours Media
Opening from the Hours of Catherine of Cleves, c. 1440, with Catherine kneeling before the Virgin and Child, surrounded by her family heraldry. Opposite is the start of Matins in the Little Office, illustrated by the Annunciation to Joachim, as the start of a long cycle of the Life of the Virgin.
Example of a more affordable and thus more common book of hours: Excerpt from a "simple" Middle Dutch book of hours. Made in the 2nd half of the fifteenth century in Brabant.
Black Hours, Morgan MS 493, Pentecost, Folios 18v/19r, c. 1475–80. Morgan Library & Museum, New York
A full-page miniature of May, from a calendar cycle by Simon Bening, early 16th century.
The Visconti Hours