Romance novels are divided into two sub-sets, category romances, also known as series romances, and single title romances.[1] Many authors write only within one of the formats, but others, including Jayne Ann Krentz and Jennifer Crusie, have achieved success in both formats.[14]
[edit] Category romance
Category romances are short, usually no more than 200 pages, or about 55,000 words.[15][16] The books are published in clearly delineated lines, with a certain number of books published in each line every month. In many cases, the books are numbered sequentially within the line.[1] These novels have widespread distribution—often worldwide—but a single U.S. print run, remaining on a bookseller's shelves until they are sold out or until the next month's titles are released and take their place.[14] Writers for the largest publisher of category romance, Harlequin/Mills & Boon, can find their novels translated into 26 languages and sold in over 100 international markets.[17]
To write a successful novel of this length, the "author must pare the story down to its essentials. Subplots and minor characters are eliminated or relegated to the backstory."[16] Nonetheless, category romance lines each have a distinct identity which may involve similar settings, characters, time periods, levels of sensuality, or types of conflict. Publishers of category romances usually issue guidelines for each line, specifying the elements necessary for a novel to be included in each line.[18][19][20] Depending on the current market and perceived reader preferences, publishers frequently begin new lines or end existing ones. Most recently, erotic and Christian lines have been introduced while traditional Regency romance lines have ended.[21]
[edit] Single title romances
Romance novels which are not published as part of a publisher's category are known as single-title novels. These novels are longer than category romances and average between 350 and 400 pages.[15] Publishers may release the novels over a shorter space of time for sales velocity and publicity reasons, but on average authors write 1.5 novels per year and have one each year published.[2][22] Single-title novels remain on the booksellers' shelves at the discretion of the store.[23]
Despite their name, single-title novels are not always stand-alone novels. Some authors prefer to write several interconnected books, ranging in number from trilogies to long-running series, so that they can revisit characters or worlds. Such sets of books often have similar titles, and may be labelled as "Number 1 in the XXX Series", but they are not considered series romances because they are not part of a particular line.[24]
http://en.wikipedia.org/wiki/Romance_novel