I write an essay at irregular intervals to display the bankrupt state of my knowledge on the writing of fiction. It is an exercise in humility.
Writing is all about the reading experience. In the best case the writer and the reader share a mystical bond. This is the immortal essence of writing and reading. I can not say if there is a written work for every reader or a reader for every written work; reading and writing are intensely personal experiences. Perhaps there are voices that will never find a listener and there are those who listen for voices they shall never hear.
There are ready made readers for particular literary tropes: detective, thriller, mystery, science fiction, fantasy, romance, horror, et. al. There are narrow readers who venture within a few tropes and there are the magnificent, omnivorous readers of voracious appetite and nuanced taste who span the breadth, scale the heights and plum the depths that fiction has to offer.
There are writers who labor like lonely monks offering prayers to an indifferent god, iconoclasts that care not for readers or publishers, but there are many who wish the approbation and confirmation offered by that critical mass of readers that can turn a profit for a publisher. And they do not write for the money - only a very, very few make more money per hour than a burger flipper at McDonald's. A universe of trenchant commentary on the sad state of commercial writing can be can be summarized by simply noting that most writing associations consider a piece to be professional if it sells for at least a nickel a word. [In a wonderful little movie from 1947, a publisher tells an aspiring writer who has just turned down a generous offer: "You know, some of the boys are writing for only a nickel a word." A nickel in 1947 is probably worth more than a dollar now.]
Writing for mass readership is ultimately an exercise in reader psychology. Psychology in general is a "science" in which almost nothing is known. Lost in Freud and Jung and other "personality cults", psychology possesses a slender claim on science, reader psycholgy even less so. In that little tome called The Elements of Style, Strunk and white make the assertion that the passive voice is less dynamic and forceful than the active voice and should therefore be avoided. This is an assertion about reader psychology and is one of the few extant. Anything that can be said of commercial writing excepting its physical act is a claim about reader psychology. Everything that follows should be interpreted in that light.
Story is paramount; story is king; story can carry a work of fiction despite shortcomings in style. Story is not omnipotent; difficult prose, a sufficiently irritating voice, or large amounts of tedium can all destroy a good story, but good writing (whatever it might be) begins and ends with a good story. (But what makes a good story? Ah....)
Writing, in its entirety, is the story and the manner of it's telling. The manner of telling includes everything that ain't story: voice, prose style, the order of the telling, things unnumbered. The best manner of telling is that which allows the reader to become immersed in the story, oblivious to all else.
Of course what separates good fiction from the truly great is theme. It can be an obvious comment on social injustice (Dickens) or something definite but subtle, just out of reach (Fitzgerald's The Great Gatsby). Where is theme, you ask. There is a simple answer; it's in the story.
So, what is my advice for the aspiring writer?
1. Don't quit your day job.
2. Spend all your thought and effort on story. Make sure you have a really good story.
3. If you discern an underlying theme, enchance it, but don't beat it to death.
4. Use good serviceable prose that's simple and direct. Avoid anything that focuses the attention of the reader on the prose instead of the story (e.g., intricate or inverted sentence structure). The reader should glide unimpeded through the prose. Henry James would be much more widely admired for his wonderful stories if had told them in something other than tediously Latinesque prose.
5. Avoid tedium. Commercial fiction is written for entertainment (tedium and entertainment are antonyms). Sufficient tedium can destry even the best story (e.g., Du Maurier's Rebecca - you could cut a hundred pages out of it and leave it brilliantly intact but more focused).
So there we have it. Now we can all be good commercial writers. Oh...except for that story thing...oh yeah, and that reader psychology thing and...who knows what else.