blue book valuenoun [ C or U ]
also Blue Book value uk/ˌbluː ˈbʊk ˌvæl.juː//ˌbluː ˈbʊk ˌvæl.juː/USthe official value of a used (= not new) car, usually according to a published list called the Kelley Blue Book:
He paid thousands more than Blue Book value for an old car from the dealership.