book of account vs account book

book of account and account book both are nouns.

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

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

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

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

book of account (noun)	account book (noun)
a record in which commercial accounts are recorded	a record in which commercial accounts are recorded