Holy Writ vs Book

Holy Writ and Book both are nouns.

Word	Noun	Adjective	Verb	Adverb
Holy Writ	Yes	No	No	No
Book	Yes	No	No	No

As nouns, Holy Writ and Book are synonyms defined as:

Other synonyms of Holy Writ include Bible, Christian Bible, Good Book, Holy Scripture, Scripture, Word, Word of God.

Holy Writ (noun)	Book (noun)
the sacred writings of the Christian religions	the sacred writings of the Christian religions
	the sacred writings of Islam revealed by God to the prophet Muhammad during his life at Mecca and Medina