Why am I writing an article about reading for aspiring fiction writers? Because once you become a writer, you'll never be "just a reader" again. Every time you open a book -- any book, as Faulkner said above -- you'll be walking into a classroom.
Look at your favorite books. Why are they your favorites? What is it about that story that appeals to you, while other stories leave you cold, or disliking them? I don't want you to dismiss this question with a shrug and "It's fantasy. I like fantasy." I want you to decide exactly what details of that story made you like it above others you read. The characters -- how they behaved or the way they spoke to one another? The interesting or exciting or intriguing events that unfolded in the course of the story, so you couldn't put it down? The feeling that you were right there with the characters, or that you knew them really, really well? Or because someone else felt the same way or thought the same things you do, and wrote them down in a way that made you think, "Yes, that's exactly right!"
Someone made that book your favorite. Its author drew on skill, technique, and his or her own emotions and experiences to make the story come alive for you. It was no accident. That was the work of the writer.
Looking at your favorite story with that in mind puts a whole new twist on it, doesn't it? Goodbye, reader; enter writer-in-training.
So, now that you know you liked the characters, say, because the writer made them likeable, look at how he or she did that. Look at the bad guys too, realizing that the writer wanted them to be unlikable. Think about every detail you learned about the characters. Reread the story and pay attention to every instance where you learn something about the characters, where they do something that lets you get to know them a little bit more. Look at the writing in these spots: the word choices, how the character is described, what the character does or says. Pay attention to how you feel when you read these details about the character, and then try to figure out why.
Apply this to every aspect of the story. If at some point you could vividly imagine the sounds and smells and the overall squalor of a tenement in Victorian London, stop reading and examine the words and descriptions the author uses to bring it to life in your mind. If you feel your pulse speed up with excitement or your shoulders tighten with tension or you become very curious, stop and examine the writing at that point and try to figure out what the author did to make you feel that way.
Do this with every story you read. If you hate a story, examine it to figure out why -- what, exactly, you didn't like. You'll be learning from others' mistakes -- or, if it's a matter of taste rather than error, you'll learn what type of writing does not appeal to you. This, applied subconsciously as you write, will contribute to the gradual development of your own writing style.
After a while, you'll do this automatically. You'll be absorbing and learning every time you read.
What else can you learn from reading? If you prefer a certain genre, such as mystery or romance or thriller, reading widely in that genre -- both contemporary and past offerings, by many authors -- will tell you what's already been done, how it's been done, and whether it's been done to death already.
By reading what's been done well already, you will learn technique; by reading voraciously, you'll develop an understanding of the conventions of your chosen genre so you can write more effectively within that genre yourself; by reading contemporary offerings, you'll gain an understanding of the market that will enable you to pitch your own stories more effectively. However, don't read for trends.
Consider these scenarios. Say you have a story idea about Mars, an idea so original, you're sure it will be a hit with publishers. But when you send it to publishers, it's rejected again and again. Perhaps one rejection will include a scribbled "Unoriginal. Already done." Belatedly, you investigate, only to discover that everyone from C.S. Lewis to Kim Stanley Robinson has written about Mars. If you had read widely in your genre, you might never have written that story now languishing in your drawer, or you would have slanted your story in such a way that it was truly fresh in an arena where Mars has been "done to death."
"But I've read everything," you think, "and there are tons of stories about wizards being published right now. I have an idea for a wizard story just like those -- that one will get published."
Don't count on it. The stories you're reading now were purchased months and months ago. Publishers will have moved on to other things. Read to learn, not to jump on a bandwagon that rolled by last year.
Read everything, Faulkner said above, and well you should. Read outside your genre. That romance novel you disdain now could offer you valuable insights into technique when you're faced with a love scene in your murder mystery. Read nonfiction as well as fiction. Many successful writers, including Shakespeare, drew on history and mythology for story ideas. That obscure piece in the morning newspaper may give you an idea for a story. An article on ladies' fashions in Elizabethan England could provide you with the details that bring your historical fiction to life.
Read novels and read short stories; read poetry. Poetry will tune your writer's ear to the rhythm of language, and make your writing beautiful. Novels and short stories each have their own technical requirements; studying overall story arc in a novel will teach you about plot and structure; the length restrictions imposed by short stories will both allow you to study technique in condensed form and teach you how such important aspects as characterization and setting can be conveyed to maximum effect in a minimum of space.
Have I convinced you yet? Good! Now pick up a book, and start learning how to write.