From what I've gathered from courses in the past, literature sometimes looks into a work with more meaning than a writer may have originally intended. (And I can tell you from personal experience that I've had people read way too much into my own writing.) Now one may ask themselves why study literature if the interpretation may overreach the intention. One answer may be that writers don't always know what the hell they are doing and they need someone else to tell them what they've created, but a better answer would be that examination gives the work meaning.
Let's look at this using the legal metaphor. For example, the First Amendment was written in the late 1700's:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.
For some people, this is very straight forward; but for many others, the Amendment needs interpretation, hence the need for courts and lawyers, etc. Some have an odd interpretation of the Amendment (I've had one guy tell me that Congress doesn't have a right to legislate because the First says, "Congress shall make no law," failing to realize that there was more to that sentence - not a very bright guy, but he said that he kept a copy of the Constitution in his pocket at all times. I guess Article I was missing from his copy. Fuckin' weirdo.) Now, did the framers of the Constitution have Hustler Magazine v. Jerry Falwell in mind when they wrote the law? I seriously doubt it, but it further defined the Amendment (and gave us a Milos Foreman movie, giving Courtney Love some respectablility, and then giving her an opportunity to squander that respect to become the drug addict mess that we've all come to love. Oh, and to give her an excuse to further destory the memory of Kurt Cobain. But I digress).
Literature does the same for the written word. If one were to write about a girl struggling wth some major decision while living in a small town, someone else may come along and interpret the story as a statement on feminism in America. Is this the original intent of the story? One doesn't know unless the writer expresses his/her intention. And believe me, there are plenty of literary writers who are more than happy to tell you how to read their stories.
But the trouble of interpretation is that it sometimes leads one to see something that itsn't there. Sometimes a cigar is just a cigar, as Freud said. I remember one workshop in which a lot of the participants wanted to know the meaning of a bee hive in one person's story. They argued that if it had no meaning, than it had to go; which is ridiculous. The bees were there so the boy in the story would get stung. If every word needed meaning, then who the hell would take the time to write?
So, you may ask, should crime fiction be studied in literature; at which point I smack you over the head and call you a moron - of course crime fiction deserves to be interpreted. But how many crime fiction stories and novels do you see on literature class syllabi? Not many, if at all. Is this a good thing? Well, on one hand it suggests that such popular fiction isn't respectible enough for consideration by academia; but on the other hand, how many people have been turned off by English classes?