What is the origin of the idiom "by the book" and when to use it?

The origin of the idiom "by the book" draws from the idea of following instructions or guidelines found in a book or manual, which can be traced back to ancient times. This phrase may have gained prominence during the 19th century, as the use of written rules and regulations became more widespread in various fields. It is commonly used in discussions related to law, regulations, policies, and professional practices.