Books are wonderful resources for research, because they contain a lot of information but can reach broader and deeper than articles. Books can actually be somewhat like a collection of articles on a topic, but there's always a strong thread tying the information, methodologies, and conclusions together.
When searching for books, use SUBJECTS to navigate between books that cover the same topics. You can find SUBJECT links in the catalog record below the shelf and basic bibliographic (title, author, publication) information. For example, this copy of The Crucible has a subject of "Witchcraft in literature" which connects to more books about the play, but also books about 17th century English magic to Anne Rice novels.
You can also use SUBJECT searches to find books ABOUT instead of BY a playwright. For example, if you search for MILLER, ARTHUR as a subject instead of as an author, you'll get books ABOUT him, not plays BY him. You might get a few plays, but they probably include essays or other introductory material ABOUT Miller.
Found a book that appears highly relevant to your research? Be sure to look at other books in the same virtual or physical space. If you grab the book off the shelf in the library, the books on either side should be related to your book by SUBJECT. You can browse the shelf in the book's catalog record by scrolling to the bottom of the record and looking for the "shelf," then you can navigate the shelf using the arrows.
The Libraries subscribes to hundreds of databases with articles that can inform your research. How to pick the right database for your needs? Here are some recommendations, and a link to the full list so you can explore it using keyword searching or filters for subject, type, and vendor.
Looking for Newspapers and Magazines? Check out the Primary Sources page on this guide.