Every noblewoman had hers, from the thirteenth century onwards, and depending on her wealth, it was more or less decorated and illuminated with more or less art. Mary of Guise’s Book of Hours, a XVth century manuscript, comes from St. Benedict’s Abbey, Fort Augustus, and is kept now in the National Library of Scotland.
"Of manuscripts acquired at a later date by the abbey at Fort Augustus some of the most interesting are (…) a 15th-century Book of Hours that belonged to Mary of Guise, Queen Consort of James V. The Book of Hours was given by Lord Ralph Kerr, third son of the 7th Marquess of Lothian, who also presented six printed books." (NLS website)
As Belinda Jack puts it in her book "The Woman Reader", Books of Hours are "liturgical scrapbooks, hotchpotches made up of the ‘Little Office of the Blessed Virgin Mary’ (a collation of brief services) designed to be said at various points throughout the day, and including psalms, hymns, prayers and, very often, a calendar of saints." (Yale University Press, 2012, p. 94)
The only page of Mary’s Book of Hours avaliable online is that of a calendar of saints; we note in red "epiphania domini", latin for Epiphany, which is celebrated on january 6th. Underneath the calendar, Mary has apposed in her hand her name, "Marie", and the letter "R" for regina, latin for queen. Mary of Lorraine has been crowned queen consort of Scotland on february 22, 1540 at Holyrood Abbey, which at that time lay outside the city of Edinburgh. Her handwriting might date from that year.
Mary of Lorraine could have brought her Book of Hours over from France when she came to Scotland two years earlier. The Book dating from the XVth century, it may mean that she inherited it from her mother Antoinette of Bourbon, or even more so her grandmother, the very pious Philippa of Guelders, who died in very old age in 1547.