gen. A book containing rules, or a body of rules or regulations. Obsolete.

A book of rulings, rules, or regulations. In later use frequently figurative with reference to accustomed or conventional behaviour.

a book containing rules or regulations concerning a particular matter or for a specific organization; also figurative in later use; = rule book, n.

With the. A (notional) rule book or instruction manual; (hence) the way things are usually or conventionally done. See also by the book at phrases 2e.

(a) the libretto of an opera, etc. (cf. sense 10b); (b) colloquial any written or printed record or set of rules or instructions; also in…