A book is the emblem of St Anne, St Augustine, St Bernard, and other saints.
Recorded from Old English (in form bōc, originally meaning also ‘a document or charter’), the word is of Germanic origin, and is probably related to beech (on which runes were carved).
Book of Common Prayer the official service book of the Church of England, compiled by Thomas Cranmer and others, first issued in 1549, and largely unchanged since the revision of 1662.
book of hours a book of prayers appointed for particular canonical hours or times of day, used by Roman Catholics for private devotions and popular especially in the Middle Ages, when they were often richly illuminated.
Book of Kells an 8th-century illuminated manuscript of the Gospels, now kept in the library of Trinity College, Dublin, and produced either in the scriptorium of Iona or at Kells in County Meath, where the community moved after attack by Vikings in the early 9th century.
book of life the record of those achieving salvation; originally, with biblical reference, as in Revelation 20:12.
Book of the Dead a collection of ancient Egyptian religious and magical texts, selections from which were often written on or placed in tombs. The name (in full Tibetan Book of the Dead) is also given to a Tibetan Buddhist text recited during funerary rites, describing the passage from death to rebirth.
you can't tell a book by its cover outward appearance is not a guide to a person's real nature; saying recorded from the early 20th century.
See also a great book is a great evil, People of the Book at people, the oldest trick in the book, a turn-up for the book.