Good Book vs Word

Good Book and Word both are nouns.

Word	Noun	Adjective	Verb	Adverb
Good Book	Yes	No	No	No
Word	Yes	No	No	No

As nouns, Good Book and Word are synonyms defined as:

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

Good Book (noun)	Word (noun)
the sacred writings of the Christian religions	the sacred writings of the Christian religions
	the divine word of God; the second person in the Trinity (incarnate in Jesus)