Dictionary.net

All the volumes which contain authentic reports of decisions in English courts, from the earliest times to the present, are called, par exccllcnce, "The Books." Wharton.

Commerce, accounts. Merchants, traders, and other persons, who are desirous of understanding their affairs, and of explaining them when necessary, keep, 1. a day book; 2. a journal; 3. a ledger; 4. a letter book; 5. an invoice book; 6. a cash book; 7. a bill book; 8. a bank book; and 9. a cheek book. The reader is referred to these several articles. Commercial books are kept by single or by double entry.