Narrative Summary
Narrative summary is possibly the most flexible of the various ways of presenting a story. Narrative summary doesn't necessarily tie the author down to chronological order, the way dialog and dramatization do, nor does it require a focus on one particular aspect of the story, as description often does. This makes narrative summary at once both one of the most useful tools in a writer's toolbox, and one of the trickiest.
Basically, narrative summary is just telling some of the story in whatever way seems to make the most sense. It gets used for everything from brief transitions between scenes ("He left the office and went down to the coffee shop.") to longer summaries of what's been happening ("The next six months were hard on everyone. Even after George found the whatchamacallit and Celia figured out where it fit into the alien machine, nobody could get it working. They almost ran out of air twice when the electrolysis machine broke. Etc.").
Infodumps are chunks of narrative summary; so are most historical prologues, appendices, and those plot summaries of what happened in the previous two books of a series that crop up occasionally. Narrative summary can even crop up in dialog, as when the detective is presenting the case against the murderer, or when the guy who's been missing for a week finally shows up and fills everyone in on where he's been and what he's been doing. Bits of narrative summary can be embedded in the middle of dramatized scenes to provide backstory or widen the scope. Traditional fairy tales are almost nothing but narrative summary, with maybe a few lines of dialog.
All these possibilities can make it a little hard to get a handle on narrative summary, and it's complicated even more by the possibilities for stylistic variation. The style for narrative summary ranges from what's referred to as plain, simple, or invisible to detailed or even elaborate. "The elders took their places on the dais. Elder Morgan stepped forward and presented Janet's plan; after much discussion, the villagers voted in favor." is plain narrative summary; "The elders filed in and seated themselves, one by one, on the dais, their white hair gleaming in the lamplight. Elder Morgan hobbled forward, and in a creaky voice that barely carried to the rear of the hall, read the plan that Janet had cooked up. When he finished, the villagers began talking…and talking…and talking. When the elder finally called for a vote two hours later, three-quarters of the men raised their spears in favor." is more detailed and colorful, but it's still narrative summary.
When you have a brief transition or a bit of narrative summary that's embedded in a dramatized scene, it's usually (not always) most effective to stick to the plain style of narrative summary. If all you need is a brief transition to get the characters from Time-and-Place A to Time-and-Place B, "He left the office and went down to the coffee shop" will do the job. Within a scene, one generally doesn't want to bring the action to a screeching halt by suddenly calling attention to a bit of backstory, and a plain style (or one that matches the level of description in the scene, anyway) is likely to be the least noticeable.
The more lengthy the narrative summary section, however, the more interesting and memorable it needs to be in order to hold the reader's attention. "Interesting and memorable" can come from content or from providing more concrete details and making stronger word choices than one would for a plain/invisible style (and really, trying to write three pages, or even three paragraphs, of narrative summary "invisibly" is just asking for readers to skip over them). Ideally, one would do both.
For example, "Sorry, Robert," Jane said. She'd been there when Robert murdered Sam, and she wasn't about to give him reason to make her his second victim" is plain style, but if this is the first we've heard about Robert murdering someone or Jane being there, the revelation alone is plenty dramatic enough to be memorable. On the other hand, "She'd been crouched behind the sofa when Robert cut Sam's throat two years before…" isn't much longer, but it's considerably more specific and dramatic. Possibly too dramatic; if I don't want the murder and Jane's presence to overshadow what's going on in the rest of the scene, I'll stick to the plain version. If I do want this revelation to cast a long shadow, I'll opt for the second.
The plain-vs.-detail decision also applies when the writer is using narrative summary as a third alternative to the usual "show it or skip it" system that writers are so often encouraged to adopt. "For six months, they worked on the gizmo, to no avail. Finally in April, they…" makes a very fine, plain, simple transition if nothing interesting or story-relevant happens during those six months. There are at least three times when a writer may want a lot more than this single sentence, however: first, when things happen during that six-month period that are interesting and story-relevant, but not quite important enough to show in detail; second, when the writer wants the reader to have more of a sense that six months have actually gone by and the next scene can't possibly be happening two or three hours after the previous one; and third, when the writer isn't actually sure whether anything interesting or story-relevant happens in that six months and can't find out without writing more of a summary than "For six months, they worked on the gizmo."
That last is, I think, more common than a lot of writers want to admit, and the biggest problem with it is that if one writes the six-month summary and discovers that nothing really interesting or story-relevant happens after all, one has to cut it. Lots of us really, really hate doing that. When one has made up several pages of details, there are nearly always cool bits that the writer loves somewhere in there, and it is extremely hard to be clear-eyed about which of them are really needed in the story and which aren't. It's even harder to be ruthless enough to cut the ones that one dearly loves (and spent hours figuring out), even after it's become obvious that they just don't belong in this book.
