I'm looking for a pair of reference books that covers plots of English literature. I imagine if you have seen them or used them you'll know what I'm talking about. I don't remember the title or the author. Any assistance or guidance is appreciated.
I'm not sure this is the exact work you're looking for, but there's a well-known series that does plot summaries called Masterplots.
I also have a pair of similar reference books on my own shelf that are specifically for speculative fiction ("The Encyclopedia of Fantasy" and "The Encyclopedia of Science Fiction," both co-edited by John Clute, and published by St. Martin's Griffin), but it doesn't sound like you're looking for something that specific. If you are, the most recent edition came out in 2011, and is apparently now available for free, online.