Oxford Companions and Cambridge Companions are a series of authoritative guides, written by leading experts, offering introductions to major writers, artists, topics, and periods. They are an excellent resource for getting started with your research.
There are many handbooks, dictionaries, and encyclopedias that provide basic information for literary studies. If you are not clear about your topic, try establishing its limits with a good definition and some introductory information. The following sources can give you a quick overview or summary of a topic.