The "Blue Book" typically refers to a publication that provides authoritative information on a specific subject. One of the most well-known examples is the Blue Book for used car values, which helps buyers and sellers determine fair prices based on market trends. This guide is widely used in the automotive industry. Another notable example is the Blue Book of the United States Congress, which contains detailed information about the legislative process and the roles of various government officials. It serves as a reference for understanding the workings of the U.S. government and its functions.