At next week’s Book Expo in New York — the publishing industry’s annual orgy of optimism — Harlequin is set to celebrate its newest imprint: Cosmo Red-Hot Reads.

The series promises “love scenes that are frequent, fun, detailed, fantasy-oriented and push the envelope.”

This is a major new e-book line produced in conjunction with Cosmopolitan magazine. To launch the series, Harlequin spent at least $1 million for two stories from best-selling romance author Sylvia Day.

That sounds like a “fantasy-oriented” financial extravagance, but Malle Vallik, director of digital editorial at Harlequin, says Day is key to getting the series launched effectively.

“We invested a lot, yes,” Vallik says from her office in Toronto. “We’re incredibly confident about this brand. We knew what Sylvia would be delivering, and she has delivered. She’s at the top of her game and on the rise.”

Starting this August with Day’s “Afterburn” ($3.99), Harlequin plans to publish two Red-Hot Reads every month. (The company already publishes about 110 titles every month.) Each of these “Red-Hot” e-books, written by a stable of new and established authors, will run about 30,000 words, filling a space in the market between short stories and novels.

The company considers that length essential to the success of the series. “Thirty thousand is really a great length for a book,” Vallik says. “You get a great story that you can read in an evening.”

Vallik says the “Red-Hot Reads” will have the sensibility of HBO’s “Girls” — “but less whiny and with much better sex.” Like the protagonists in Lena Dunham’s TV show, Harlequin’s protagonists will be in their 20s. “The voices are just really current. They’re living in the big city. A man isn’t necessary to make them happy — he’s the icing on the cake.”

Vallik says that Harlequin will eventually consider a variety of formats for these novellas. Some may later be republished as bound singles or in collections. That’s an opportunity to keep traditional booksellers in the loop.

The partnership with Cosmopolitan offered Harlequin a chance to reach a younger audience. And the magazine wanted a book partner that knew the romance world.

Cosmo book editor John Searles is working closely with Vallik. “There’s a marketing meeting every week to talk about what we’ll be doing — looking at the packaging, making sure everybody’s happy,” Vallik says.

From the looks of most Harlequin covers, everybody’s happy indeed.

Twitter @RonCharles