Good Book vs Christian Bible

Good Book and Christian Bible both are nouns.

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

As nouns, Good Book and Christian Bible are synonyms defined as:

Good Book and Christian Bible: the sacred writings of the Christian religions

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

Good Book (noun)	Christian Bible (noun)
the sacred writings of the Christian religions	the sacred writings of the Christian religions