A reader asks:
How much description or dialog that may be “unnecessary” to the plot is acceptable if it contributes to “atmosphere” or characterization?
Short answer: Nothing “unnecessary” belongs in your novel.
But this reader’s question is not about padding his novel with “unnecessary” dialog. The question is really one of proportion. What proportion of the book can be allotted to atomosphere and characterization compared to plot advancement?
In some genres, the plot may be the most important element. In others, character is of more interest to the reader.
Whatever the genre, however, the story is more than the plot. If your dialog establishes atmosphere and characterization, it will contribute at the same time to the plot.
How much dialog and what kind will be determined by genre and personal style.
A page of P.D. James is denser than a page of Elmore Leonard. Some pages in a Leonard novel have so much white space you might think you’re looking at the script for a play. James, on the other hand, will give one speaker a brief line and have the other speaker respond with a paragraph. The result is that a page of her dialog resembles a page of narrative.
At a guess, I’d think that for most modern writers, the narrative:dialog ratio is about 50:50. Some of the dialog will advance the plot. Some of it will establish character. Ideally, all the dialog will do some of both.
Since most of us write the kind of books we like to read, it can be helpful to analyze the work of favorite authors to see how they do it. And keep your target audience in mind. Readers who love Elmore Leonard may not go for P.D. James.
Leonard, who writes very lean prose, has formulated 10 Writing Tips for writers who would like to emulate him. You can find them here.