encyclopaedia vs book of facts

encyclopaedia and book of facts both are nouns.

Word	Noun	Adjective	Verb	Adverb
encyclopaedia	Yes	No	No	No
book of facts	Yes	No	No	No

As nouns, book of facts is a hypernym of encyclopaedia; that is, book of facts is a word with a broader meaning than encyclopaedia:

encyclopaedia: a reference work (often in several volumes) containing articles on various topics (often arranged in alphabetical order) dealing with the entire range of human knowledge or with some particular specialty
book of facts: a book to which you can refer for authoritative facts

Other hypernyms of encyclopaedia include reference, reference book, reference work.

encyclopaedia (noun)	book of facts (noun)
a reference work (often in several volumes) containing articles on various topics (often arranged in alphabetical order) dealing with the entire range of human knowledge or with some particular specialty	a book to which you can refer for authoritative facts