First of all, fiction divides into literary and commercial.
Commercial fiction is broad and covers subgenres such as mystery, romance, legal thriller, western, science fiction, and so on.
Examples: John Grisham, Sidney Sheldon, Danielle Steele, and Jackie Collins.
Literary fiction appeals to a smaller audience. It can fall into subgenres but excellent writing, originality of thought, and unusual style makes it different from commercial fiction.
Example: Charles Frazier, Toni Morrision, Barbara Kingsolver, John LeCarre, and Saul Bellow.
Mainstream fiction describes both commercial and literary works. Usually set in the 20th or present-day 21st century and with a universal theme such as family issues, coming of age initiations, courtroom dramas, career matters, physical and mental disabilities, social pressures, political intrigue, and more. Regardless of original genre or category, most of the novels that appear on the bestseller list are considered mainstream, whether the author is Sue Grafton, Arundhati Roy, Michael Crichton, or David Guterson.
Popular fiction has defined categories of appeal to specific audiences. These are classed as genre fiction, each with its own set of rules and conventions.
Mysteries focus on a crime, usually murder. subgenres include spy, detective, and crime stories. Examples: Carl Hiaason, James Ellroy, Robert Parker, James Lee Burke, and Elmore Leonard.
Romance, the largest, most diverse, and most popular of the commercial genres diverts and entertains women. Romance novels contain elements of fantasy, love, naïveté, extravagance, adventure, and a hero who overcomes impossible odds to be with his true love. Subgenres of romance include regency, historical, bodice rippers, and contemporary. For historical detail and settings, read a regency or historical romance. For tempestuous relationships you want bodice rippers .
Example: Barbara Cartland, Jude Deveraux, Victoria Holt, Daphne Du Maurier, and Danielle Steele.
Publishers and booksellers have identified a category within the mainstream that they classify as Women's Fiction. Some key characteristics include a focus on relationships, one or more strong female protagonists, women triumphing over unbearable circumstances, and the experiences of women unified in some way.
Examples: Barbara Taylor Bradford, Anne Rivers Siddons, Alice McDermott, Judith Krantz, Anne Tyler, Rebecca Wells, and Alice Hoffman.
Category fiction is often used as a synonym for genre fiction such as Westerns or Thrillers. " Category romance are short and published in clearly marked categories, often labelled sequentially. Harlequin/Mills & Boon is the biggest publisher of category romances, releasing 500 titles a month in 25 different languages.