Good for brief references. Revised 5th edition. The Oxford Companions are a browser's delight as well as a valuable aid in research. There are articles on authors, literary works and movements, characters, genres, forms, etc. It's worth having one on your desk.
Earlier editions provide insight into literary and critical fashion and canon formation.
Cambridge Guide to Fiction in English . Encyclopedia of American Literature . Similar to the Oxford Companions but featuring somewhat longer articles on authors, genres, and movements. These works are similar to the Oxford Companions cited above, but with a more restricted focus. Cambridge Companion to English Literature , 1650-1740.