A casebook is a textbook for a law school course. It often contains extensive excerpts from important cases, relevant statutes, journal articles, and other secondary sources as well as commentary from the casebook author. For research purposes, a casebook can be used to get a general overview of the law and a sense of the most important issues in the field. To build on information located in a casebook, use a citator (Shepard's on LexisNexis or KeyCite on Westlaw) or search for other books or articles written by excerpted authors.
These sources are aimed particularly at practicing lawyers who need to have quick access to the current information in a particular area of law. They are released or updated frequently and generally contain primary documents (statutes, regulations, and cases) as well as news, articles, and summaries of recent developments.