What is Bill-book?

Legal Definition
In mercantile law. A book in which an account of bills of exchange and promissory notes, whether payable or receivable, is stated.
Legal Definition
Commerce, accounts. One in in which an account is kept of promissory notes, bills of exchange, and other bills payable or receivable: it ought to contain all that a man issues or receives. The book should show the date of the bill, the term it has to run before it becomes due, the names of all the parties to it, and the time of its becoming due, together with the amount for which it was given.
-- Bouviers Law Dictionary