There are several reference resources online. Databases like Oxford Reference will search your subject term and then offer entries from different books.
Oxford Reference is a database consisting of over 180 reference books including titles such as The Oxford Companion to Classical Literature and The Oxford Companion to English Literature . Entries are fairly descriptive but lack interpretation of the literature.
This includes reference books such as Supernatural Literature and Classical and Medieval Literature Criticism with articles that analyze themes. In addition search results include scholarly journals and articles from general resources.
