novelist vs author

novelist and author both are nouns.

Word	Noun	Adjective	Verb	Adverb
novelist	Yes	No	No	No
author	Yes	No	Yes	No

As nouns, author is a hypernym of novelist; that is, author is a word with a broader meaning than novelist:

novelist: one who writes novels
author: writes (books or stories or articles or the like) professionally (for pay)

Other hypernyms of novelist include writer.

novelist (noun)	author (noun)
one who writes novels	writes (books or stories or articles or the like) professionally (for pay)
	someone who originates or causes or initiates something

novelist (verb)	author (verb)
	be the author of