handbook vs manual

handbook and manual both are nouns.

Word	Noun	Adjective	Verb	Adverb
handbook	Yes	No	No	No
manual	Yes	Yes	No	No

As nouns, manual is a hyponym of handbook; that is, manual is a word with a more specific, narrower meaning than handbook:

handbook: a concise reference book providing specific information about a subject or location
manual: a small handbook

Other hyponyms of handbook include bible, guide, guidebook, ready reckoner, reckoner.

handbook (noun)	manual (noun)
a concise reference book providing specific information about a subject or location	(military) a prescribed drill in handling a rifle
	a small handbook

handbook (adjective)	manual (adjective)
	requiring human effort
	of or relating to the hands
	doing or requiring physical work