Inside the breast of mild-mannered suburban accountant Helen Brenna beats the passionate heart of a romantic. Good thing, too, since she left accounting a few years back to make a living off that passion.

One afternoon in 1991 she was at home taking care of her first baby, reading one Harlequin romance after another, when she set her book down and said, "I could do that."

Turns out that, yeah, she could.

Brenna, 48, is one of 1,100 romance writers sprinkled across the United States, Canada and the globe who feed the ravenous beast that is Harlequin Enterprises. She has published eight books, with her ninth coming out in June and her 10th scheduled for November. (But she has to finish writing it first.)

In these years of dwindling readership and declining book sales, Toronto-based Harlequin is soaring. The company that began in Winnipeg in 1949 publishing 25-cent mysteries, westerns and romances has turned into a focused machine, pumping out more than 110 books a month, more than 1,300 books a year, all care-fully scripted and aimed squarely at women. They have sold nearly 6 billion books, 130 million of them in 2009.

A driving force of fantasy

Brenna writes in an airy space on the second floor of the Plymouth house she shares with her husband. A railing allows her to look down at the first floor. (More useful when their two children were small.) Framed covers of some of her books -- "Treasure," "First Come Twins," "Dad For Life" -- hang on one wall, and by the computer she has taped a hand-scrawled map of the mythical Mirabelle Island in Lake Superior, where some of her adventures take place. (She envisions it as a cross between two real islands -- Mackinac and Madeline.)

She also has pasted up photographs of actress Kirsten Dunst and a shirtless, bearded actor named Oded Fehr, the physical inspirations for her current hero and heroine.

"I try not to focus too much on how someone looks," Brenna said, "but it is a fantasy, so why not have fun with it?"

Fantasy is the driving force behind Harlequin, which publishes more than 20 lines of romances, each one designed for a specific audience, ranging from religious (Steeple Hill) to erotic (Blaze). There is a NASCAR line, a medical-romance line, a line set in exotic locales. Each is instantly recognizable by its distinct cover design, and the authors follow firm guidelines. Romance readers like to know what they're getting.

"We created a promise to the reader," said Wanda Ottewell, senior editor for Harlequin Super Romance, the line Brenna writes for. "So when she picks up a Super Romance, for example, she'll find a believable, layered story, with characters who are people you'd be friends with. It will look familiar to your world. No princes or princesses, no shape-shifters." (The princes and princess you will find in the historical-fiction line, and the shape-shifters dwell over in the Luna line.)

Each line produces a certain number of books a month, and, like comic books, they come with a 30-day expiration date. After a month, they're pulled off the shelves and replaced with new titles. The paperback books are inexpensive -- about $5 -- and are sold in supermarkets, convenience stores, drugstores and newsstands in addition to bookstores. They're available as e-books and from the Harlequin website.

But even with guidelines, the books aren't necessarily easy to write. It took Brenna years to achieve success. Between the afternoon that she decided "I could do that" and the 2007 publication of her first novel, "Treasure," were many manuscripts, two agents, hope (being named a finalist three times for the "Golden Heart" award for unpublished books), despair (repeated rejections) and many, many rewrites.

"The accountant side of me was saying, 'This isn't going to work,'" she said. "I was all set to go back into accounting when I sold that first book. And then, once you sell that first book, it's like, well, after all this work I'm not going to walk away from this, even though it's been so hard. I'm going to see if I can make a go of it."

That first book earned her an advance of $5,000 and won a RITA award from the Romance Writers of America, "an amazing vote of confidence," she said. The encouragement was more than enough to keep her going.

Guilty pleasure

For some, Harlequin romances might be guilty pleasures, fast reads where love prevails and every ending is happy. But for Brenna, they're a business, and she applies the diligence of an accountant to her day. "I try to stay pretty consistent," she said. She's at her desk as early as 7 a.m. and tries to get in as much writing time as she can before her son gets home from school in mid-afternoon. Some days, she said, she's writing right up until 5 p.m.

She writes three books a year, which means producing between five and seven pages a day. "I have to really stick at it. I'll get up and come down and make a cup of tea or do a load of laundry, or take the dogs for a walk, but I'm thinking while I'm doing it, I'm thinking all the time -- when I'm driving, when I'm cooking, thinking about what's supposed to happen next."

Ottewell has a stable of about 25 writers, some of whom she has worked with for years. "It can take some backing and forthing between an author and an editor to get the story right," she said. "Book publication is not a fast process. This is genre fiction, and there are certain expectations that readers bring to the story and we have to make sure we deliver. We also want to ensure that each story is a satisfying and enjoyable read. If it's not, readers aren't going to keep reading our books."

Brenna wrestles with honing the plot twists and mysteries of her romantic adventures, spending nearly as much time revising as she does producing the first draft. "I see plots everywhere," she said. "What's hard is figuring out a plot that will sustain a book. There's always an arc -- in literary fiction, in mysteries. In a romance, it's an arc that lets the main characters fall in love.

"The power of love transforming -- that's what romances are all about."

Laurie Hertzel is the Star Tribune books editor.