A more thorough explanation:

A Blue Book is a type of publication that can have different meanings depending on the context. Here are some examples:

A Blue Book can refer to a compilation of session laws. Session laws are the laws passed during a particular session of a legislative body, such as a state or federal legislature. The Blue Book would contain all the session laws passed during a specific period of time.

Example: The Blue Book for the 2021 session of the California State Legislature contains all the laws passed during that session.

A Blue Book can also refer to a volume that provides parallel citation tables for a volume in the National Reporter System. The National Reporter System is a collection of legal cases from various courts in the United States.

Example: The Blue Book for the West's Federal Supplement contains tables that show how the cases in that volume can be cited in other legal publications.

In English law, a Blue Book is a government publication that is issued in a blue paper cover. These publications can include reports from Royal Commissions, which are groups appointed by the government to investigate specific issues and make recommendations.

Example: The Report of the Royal Commission on the Poor Laws and Relief of Distress 1905-09 is a Blue Book that contains the findings and recommendations of the commission.

Overall, a Blue Book can refer to different types of publications depending on the context, but they all share the characteristic of being published in a blue cover.