account book vs ledger

account book and ledger both are nouns.

Word	Noun	Adjective	Verb	Adverb
account book	Yes	No	No	No
ledger	Yes	No	No	No

As nouns, account book and ledger are synonyms defined as:

account book and ledger: a record in which commercial accounts are recorded

Other synonyms of account book include book, book of account, leger.

account book (noun)	ledger (noun)
a record in which commercial accounts are recorded	an accounting journal as a physical object
	a record in which commercial accounts are recorded