I'm gonna have to mostly go with Khar here. I don't care what the living person who got paid (probably) for a literary work thought or thinks, and neither should you.
The main thing that makes a work literature in my mind is that I don't care about the author's intent. When Stephen's mother writes him a letter that says "I've been trying to call, is everything ok?" We care what she thinks, and what she means, it is not literature. Newspaper opinion piece, not literature, because with each sentence I am trying to figure out what the
writer means, not what the
words mean. Book explaining Battle X in the American Civil war, same; I want to understand what the author wants me to understand. I am reading this as a form of communications between them and me. Hopefully their skill in crafting sentences allows me to understand them easily. Trashy novel telling me a story to entertain me, I care that I am understanding the plot points which the writer is trying to communicate.
Literature expands past what one person in its creation thought it meant and allows for a deeper analysis of what the work actually says. Literature tells us something more than what is on the surface, but I'm with Khar, that need not have been the author's intention. That Civil War book? maybe in 200 years someone else will read it and be fascinated by the message that is between the lines, a message which I was unable to see since I was too close to it (close in time and culture perhaps). In literary studies we read all sorts of crap that is OLD, but not fiction, things which we can now analyze differently because we were not the author's intended audience. Some people think that is bullshit though. Frequently authors try too hard to communicate a message, and in making sure that I get their point, they destroy the literary aspect of their work, American social protest theater from the early 1900's? trash. Ayn Ryand? trash.
My major problem with trying to find the author's meaning in a work is that in many (all?) cases the "author" is invented. Someone mentioned ghost writers before, and that is one example, but sometimes it gets more complex than that.
What happens when you print a work after the author's death?
Shakespreare: Shakespeare was not involved in the collecting and publishing of "his" works; they were published 7 years after his death. Let's ignore the arguments about who the "real" Shakespeare was, and only focus on the fact that whoever he was he didn't approve the versions of his works which were then published. So how can I take a single line and pick it apart and then use it to tell you what a man who died nearly 400 years ago thought? The only "Shakespeare" I can talk about is the author who was created by publishing all these plays and poems under a single name. And the only thing I have to go on is those works which claim to be his.
Emily Dickinson: Dickinson is standard high school lit here and intro to lit college classes. Everyone has taken a Dickinson poem and untangled it and figured out what it means. Dickinson didn't publish her poetry. Her poetry was pretty much un-publishable really. She had all sorts of punctuation which there was no way to print, and would write two lines in one place and some of her works were more like art objects: one of her poems on
crickets was wrapped around the body of a dead cricket, you can't tell me that doesn't change it's meaning. You can't print dead cricket carcasses. She had no say in the editing of her works into printed poems, so I find it impossible to analyze them based on her intentions, but many people do. We still have her originals though, which is more than can be said for Shakespeare.
What happens when an author is alive, but they work closely with an editor?
Printing a work is not some magical process where by I create a perfect work and then Penguin typesets it and prints it. Works are edited, sometimes heavily. How do you account for the voice of the editor in analysis? I cannot remember the author's name at the moment, but an author from the last century know for is sparse style died and his wife published his manuscripts. Come to find he rambled on for ages, his editor gave him the style he is known for.
What do you do when more than one edition of a work exists?
Are we to spend all our time trying to figure out which one is "right"? Based on what? What order do The Canterbury Tales go in? There is no way we can divine which one Chaucer preferred it is a waste of time. Instead we can talk about how the order changed the work. What do you do when new editions come out? ignore the old ones?
These are all issues that don't matter if you recognize that the "author" is created by a work and not vice versa. The biological person who first arranged some words doesn't matter.