For writers of commercial fiction, understanding the established genres and the expectations of each is a matter of first importance. In commercial fiction, a genre is a category or family of writings that share similar characteristics, whether by subject matter, manner of treatment, or intended audience. Among the most common genres are romance, mystery, suspense, mainstream, historical, young adult, women's fiction, etc.
So one of the first decisions the writer must make is his selection of genre. Is the contemplated work a mystery or a suspense novel? If it is a mystery, the author will not allow the reader to know no more than the sleuth/hero. Hero and reader proceed clue by clue until, at last, the villain is unmasked. But in a suspense novel, the author shows the reader at least some of the villainous forces the hero faces. Because the reader knows more than the hero, the story focuses on the ways in which the hero discovers and overcomes the forces that threaten him. Romances have their own patterns and formulas, and at least one romance writer has the formula refined down to the exact page on which the First Kiss occurs.
I did not understand the limits of genres when I began writing for the Christian market, and the result was a great deal of wasted time and effort. My idea for a story fit snugly into the years soon after World War II and before the Cold War became established. That was my first mistake, for the time limit on the historical genre then ended with World War II.
Beyond that, in my ignorance I let the story develop organically according to each major character's interests, values, and response to the basic situation. In terms of genre, then, I had a hybrid that was neither fish nor fowl. The story had love interest, but it did not fit the genre pattern of a romance. Yet, as one agent told me, the hero and heroine were too conscious of each other for the novel to be mainstream. It also had mystery, but the reader would know much more than the hero and heroine did. It had suspense, but the elements of suspense were tempered by humor and character study.
In short, I had a novel that was only itself and did not fit into any of the established pigeonholes of publishing. Consequently, it went unpublished for years.
What changed? Publishers expanded the genre of historical fiction past World War II. Then my long-suffering agent found a publisher, Lighthouse Publishing of the Carolinas, willing to accept a novel that didn't fit nicely into any particular genre. The publisher, agent, and I were eventually rewarded by the novel, Lightning on a Quiet Night, becoming a finalist for the 2015 Selah Awards.
What can we learn from this? What I learned was to scout out each intended genre before beginning to write. How-to-do-it books like Hallie Ephron's Writing and Selling Your Mystery Novel can help, as can attending classes at writing conferences. But in the end, there is no substitute for the prospective author's extensive reading of successful novels in his intended genre.