I've read some very good stories today. One was exceptionally short - a retelling of sleeping beauty, but with an entirely different and satisfying ending. It clocked in at under 1000 words, but contained an exceptional amount of detail.
Note: It told an entire story in under 1000 words. The details that it picked were vitally important. They lent themselves to the mood, what the character noticed, and showed us how the in-story world structured itself. It showed us what was important to the characters. It lent a rhythm and cadence to the story. It also showed us what was important plot wise.
And that's probably the three most important jobs of detail in narrative: To situate and anchor the reader, to give rhythm to your paragraphs, and to tell us when to pay attention.
Firstly, on anchoring the reader:
The easiest way to explain and think about this is to compare two genres. Lets go... contemporary romance and fantasy. Say both books have Character A walking into a room and Character B waiting in the room to talk to them. You have a myriad number of things to describe, lots of narration to provide. So how much detail do you include?
Given that we're talking specifically about anchoring the reader? The fantasy is probably going to include more detail than the contemp romance. In the fantasy, I would focus on the things in the room that tell the POV character who this stranger is, maybe focus on the things that he's either wearing that can tell us about his status, how these two relate, ect.
But more than that, I can describe things to add to world-building. When my character leans up against a desk and notes with surprise that it's made of wood -because wood is generally spelled into uselessness by the woodland fae, and thus mighty expensive - that's interesting because it shows you a bit about the world, and about how the character relates to it. She hasn't treated this expensive thing in a blasé manner, so she probably can't afford it. Which means they're meeting in the room of someone wealthy, and that this conversation is probably related to those of wealth.
Note, I don't do much more in that example other than describe the table through the POV of the character, and her surprise at it being there. This piece of narrative description isn't just describing something, it's giving insight into character, the social structures of the world, the fact that this world has a magic system, and also hints at the involvement of others in this conversation about to come up. It's not just describing something - you're making those words work for you.
In the contemp romance, the details would focus more on the characters, and how they relate to the room. Whether Character B seems comfortable in the space, whether his clothes suggest something about status, or where he's been in the last five minutes. The descriptions may focus on the things the Character A finds attractive about him, or how he uses the objects in the room.
We know what a room looks like in our world. (This is presuming this contemp romance is based in a western country.) It doesn't need describing or explaining because it doesn't add anything to the story other than a detailed description. Most readers do fine with a basic description to figure out where they are and what's going on. Detail is used to try and negate that confusion and to situation the reader in the characters and the world you're creating.
This leads nicely onto my next point : detail tells the reader what is important in the scene.
Say you've just started a book. There's a basic description of a street, and then the author spends a paragraph describing an old, beaten up car; the way it's out of place, the way it hasn't moved for days, the fact that is has a myriad of scratches in the paint down the left side.
As a reader, I'm placing my bets on that car being important in some way, shape or form. I am now focused on the car. If done well, the author may have even built up some anticipation about the car.
Be aware that you are doing this when you write detailed descriptions. You are literally circling Chekov's gun on the mantle piece with red texter and tossing glitter over it. A detailed description is almost a promise to the reader.
And lastly rhythm.
Sentences, paragraphs, and chapters have a rhythm. I'll talk in one of my later posts about macro level pacing, but let's concentrate on the sentence level rhythm for the moment.
Narrative draws the inner eye of the reader. As you add detail, you're making the reader focus on what you're describing, making them slow down before you move them onto the next point. If you're descriptions are sparse of detail, the reader is going to move from one thing to the next in quick succession: bang, bang, bang. Detail, or lack of it, is something you can manipulate in a sentence to slow down or speed up the rhythm of a paragraph.
I hope that gives you some insight you haven't had before. Enjoy all,