Legal research material is typcially divided into two broad categories: primary sources and secondary sources. Primary sources are authoritative statements of the law -- statutes, courts decisions, regulations -- issued by governmental entities. Secondary sources explain, summarize or direct you to primary law and might even serve as persuasive authority when there is no primary law on point.
Many of these titles, authored by well known legal scholars, are considered the definitive, go-to resource in an area of the law. Prosser on Torts, Collier on Bankruptcy and Corbin on Contracts are just a few examples in this legal classic genre.
Many of these titles have been gradually migrating to the digital world so check for access on Bloomberg Law, LexisNexis and Westlaw. Regardless of print or electronic format, secondary resources provide timely analytical content and continue to be a key component in the process of conducting effective, efficient legal research.