Companions and handbooks are excellent sources to find an overview of a topic, an explanation of unfamiliar terms, or brief factual information on authors, plots, genres, etc. These sources provide general coverage.
The library owns many print Oxford Companions to literary authors. To find additional Oxford Companions, use the Library Catalog. A suggested search would be to search oxford companion as a phrase and add the author's last name. Limit your terms to the search field "title."