Old Testament vs Good Book

Old Testament and Good Book both are nouns.

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

Old Testament (noun)	Good Book (noun)
the collection of books comprising the sacred scripture of the Hebrews and recording their history as the chosen people; the first half of the Christian Bible	the sacred writings of the Christian religions