Many of science fiction's greatest novels are written in third-person omniscient. And this should come as no surprise, because nothing lets you depict a complex situation full of people (and creatures) with their own points of view, like a narrator who can view the whole scene from outside.
But many, many writing teachers will tell you to avoid third-person omniscient at all costs. They'll break out the pain sticks. Why is this? Because third person omnisicent is so freaking easy to mess up. And if you crash and burn with an omniscient narrator, you leave an extra-large crater. How can you write an omniscient narrator without being omniscient yourself?
Or maybe you are. One shouldn't presume, after all. Still, if you are omniscient, then you already know what I'm going to write next. (And if so, please call me. I have lots of questions.)
So why the heck would you want to use it? There are a few reasons.
First, it's easier to be funny with third person omniscient. It opens up all sorts of possibilities for juxtaposing what a character believes is going on, and what we "know" is going on. (This is also possible with other forms of narration, sure, but it's different.) There is an added layer of irony available to you with a narrator who can survey a scene, or present more than one point of view within a scene. (Gracefully.) You can also show what different people think is going on in a scene — Brian Michael Bendis indirectly struck a blow for third-person omniscient when he resurrected the thought balloon in Mighty Avengers. Knowing what a few different people are thinking at the same moment can be comedy gold.
Second, it lets you info-dump. Like a lot of the awesome powers of omniscience, this is one that you need to be careful with. But a lot of the time, providing a lot of complicated information and history of your alien planet or future world is like ripping off a band-aid. Sometimes, it's just more elegant to tell instead of showing. (Or tell while showing, like having the disembodied narrator float over and through your alien city, showing you a bird's eye view.) Some of the best infodumps involve a narrator who explains stuff in a breezy, fast way.
Third, it gives you versatility. Do you know what the difference between third-person limited and third-person omniscient is? A lot of the time, absolutely nothing. Most third-person omniscient narration feels exactly like third-person limited — except that sometimes you can pull back and show a broader view, or provide more information. (Again, this has to be done artfully, or it can throw the reader right out of the book.) And conversely, a lot of people who are writing in third-person limited will occasionally sneak in stuff that their narrator probably wasn't aware of. Third-person limited is often not as limited as it looks. (Watch a "third-person limited" novel for signs of omniscience, such as lengthy passages of scene-setting, that aren't clearly from one character's perspective. Often, "third-person limited" turns out to be omniscient if you scratch the surface.)
Fourth, you can have a narrator with a personality. A narrator who stands a little bit further outside things can comment on the action, or insert bits of information the characters may not have processed fully. Or just snark about things.
And finally, it lets you tell stories about more than one person. Like, you're telling the story of a community. They came to a planet from Earth a hundred years ago, and they faced a lot of the usual terraforming hassles — but now they're facing a huge new challenge. There's something nice about being able to write "Everybody went down to the crater to look at the remains of the crashed ship. Some of them scratching their heads, some of them weeping, and a few laughing without any particular humor to it." You can write a whole passage about what the community did — or one particular couple — without needing to provide one individual's POV.
Most of the problems that people have with the omniscient narrator come down to a lack of clarity. Which, really, is the main problem with bad narration in general. Good narration sets the scene, puts you in the moment, and allows you to identify with characters — or at least understand what feelings they're projecting. Bad narration leaves you lost, confused, or just disgusted.
Omniscient narration presents a special challenge to clarity, because you're not following one character's perceptions with a laser focus throughout the story. But it can also present a unique opportunity, if you choose to have a narrator with a strong voice. (Fairy tale narration is one example of this: "And so it was that the young maiden, who knew nothing of gamification, found herself surrounded by LARPing consultants, who are a most insidious breed.") Or you can do what I often do with third-person narration, which is to stick to tight third but occasionally — in a way that is clearly sign-posted and clearly not just a lapse in judgment — go omniscient.
But also, clarity requires discipline. Readers will be able to follow your narration more easily if any shifts are signaled by a break. The more clearly broken things up are, the more the reader will accept them. Even in a "tight third person" novel, the author will switch POVs between chapters. So you can experiment with going more granular than that — instead of having a chapter break between POVs, have a section break. And then you may be ready to try a paragraph break — with a clear transition.
Yes, really. If you have a scene where you really want to show what a few different characters are thinking, you can totally pull it off — but it's usually best not to switch POVs within a single paragraph. And don't bury the information that you've switched POVs halfway through a paragraph where people might miss it. Put it right where people can see it. Example: "Deborah, meanwhile, was smiling and waving, but she was thinking: I am going to kill that were-dolphin when I get home.")
Also, I get the impression that people sometimes think of an omniscient narrator as floating everywhere at once, looking at everything at the same time — and maybe that's how omniscience would be in real life. Probably, none of us knows for sure! (Again, if you are omniscient, please call me.)
But in fact, an omniscient narrator usually has a defined point of view — either because the narrator is choosing to follow one character for a while, or because you're treating the narrator like a camera lens. Like, for example, when you describe an alien city to your readers: the disembodied viewpoint of the narrator might start at one end of the city and then sweep down the main promenade, taking in the firepit of the Great Marauder before swerving over to take a look at the Temple of Bliss. And so on. Really well done omnisicient narrators often do feel like a camera lens, filming everything as they move around.
And this is a crucial thing about all narrators, whether they're first-person or some variety of third-person. Never forget what reader ought to be "seeing" at any given moment, especially when you're setting a scene. If you're not creating a clear image of the scene and how it's unveiled, bit by bit, then your readers won't be able to visualize it — and that, more than any failure of your narrator to contain its omniscience, will doom your writing.
One thing that can work really well is to borrow a trick from television: Follow a character as she walks through an area, and into a scene. Continue following the character as she meets with another character, and they have a conversation. And then, when the two of them separate, follow the second character instead of the first. You may have to throw in a scene break to make this seem natural — but you also may just be able to make it smooth enough for the readers to follow without a scene break.
A final note: Play fair with your readers. If you set a scene up as being from one character's point of view, it's probably best to avoid jumping out of that character's point of view without a clear transition of some sort. The main thing is to avoid the appearance that you've lost control over the narrator, or that you're just "falling out of" a particular POV by accident.
When I mention that I like third-person omniscient narrators, the most common question in response is usually, "But how do you build suspense?"
But in fact, a lot of the tricks that writers use to build suspense with a single POV can also work with third-person limited. Like, for example, the way an author will end a scene just as someone is about to be executed. The last sentence of the chapter might be "the blade swung down towards Reynolds' neck." And then we cut to a different character's POV, and when we see Reynolds five chapters later, it's revealed how the execution was stopped at the last minute. There's no reason you can't do that with an omniscient narrator.
There's also no reason an omniscient narrator needs to reveal every piece of information to the reader — after all, if you're omniscient, and you reveal everything you know, then the book will be infinitely long. You can stick to one character's POV as he walks into a scene where you know he's about to be ambushed.
Or you can go ahead and cut from the character walking into the Temple of Bliss to the hundred crack soldiers of the Great Marauder who are waiting in the balconies with their firesticks ready — and then back to the hero, walking into the line of fire. There's nothing wrong with just showing that something bad is about to happen, instead of relying on the readers to remember something they were told 100 pages ago. Although, as with anything else, subtlety and artfulness are not bad things.
The other point I want to make is that an omnisicent narrator can be unreliable, just like any other kind. Not in the sense of making mistakes, necessarily — but your narrator can't necessarily present every point of view on an issue at once. So if the narrator chooses to explore the point of view of someone who's clearly wrong about a bunch of stuff — and it's obvious to the readers that this character is dangerously or self-destructively wrong — that can work just as well as it would in tight third person.
I think that's the other thing that people assume about an omniscient narrator — power-madness and out-of-control recklessness. Your narrator will be changing POV every sentence! Your narrator will be describing everything, from every vantage point! And so on.
Which brings me back to the point I hinted at earlier — any third-person novel with multiple POVs is already doing omniscient narration, more or less. It's just that, you're using chapter breaks to keep it contained. I'm merely suggesting there are other ways to contain the omniscience — and that, in fact, sometimes mixing it up within a chapter can make your pace faster. (Because you don't have to wait three chapters to see how a different character feels about something, or to get the payoff of something.)
The other thing about omniscience is that it can distance you from the characters — third-person is already more distanced than first-person, so "tight third" is sort of a compromise that keeps you from soaring too far, to godlike heights above your characters.
It's certainly true that omniscient third person narration can be distancing — that's why it's so good for humor, which is often about seeing the ridiculousness and perversity of people from the outside.
But you can use a looser third person narrator and still help your readers identify with your characters — it just requires a lot of work on making their emotions come through and making them feel genuine. Again, a lot depends on clarity and how clearly the reader "sees" the scene. And also, it bears repeating that an omniscient narrator can delve pretty deeply into a single character, for an extended period.
The bottom line is, good narration is immersive, for the most part — and weak narration just lets the reader slide right off the surface. The key to all good narration is to help the reader experience a scene with all five senses — and sometimes a narrator who's not quite so tied down can help draw the reader in, by giving more ways in to the scene. Do not fear omniscience — once you know everything, you will know there is nothing to fear.