reference work vs reference book

reference work and reference book both are nouns.

Word	Noun	Adjective	Verb	Adverb
reference work	Yes	No	No	No
reference book	Yes	No	No	No

As nouns, reference work and reference book are synonyms defined as:

reference work and reference book: a book to which you can refer for authoritative facts

Other synonyms of reference work include book of facts, reference.

reference work (noun)	reference book (noun)
a book to which you can refer for authoritative facts	a book to which you can refer for authoritative facts