Secondary sources collect, condense, and interpret the law. They're a great place to start when you don't even know where to begin. Use the index, table of contents, or search box to locate a topic. Then, read the entry to learn about that area and find links to primary authority (statutes, regulations, cases, etc.).
Encyclopedias are a great place to begin your research. They are designed to give you a quick overview of a wide variety of topics. New York Jurisprudence succinctly states the substantive and procedural law of New York. It can be found on both Westlaw and Lexis.
Treatises are scholarly examinations of a single subject (e.g., evidence). They are more exhaustive than encyclopedias and are a great way to expand your knowledge. The Fordham Law Library curates an extensive list of New York treatises.
Practice materials are a type of treatise specifically designed for practitioners. They are concerned with the application of law and typically include forms, checklists, tips, and advice. Here are a few essential titles: