Categories have always been a slippery thing in the publishing world. While some may roll their eyes at ever-splintering genre tags, the need to use these descriptors is becoming more necessary for editors and agents. In Young Adult, the category to which two of the bestselling franchises in the past 10 years belong—Twilight and the Hunger Games—a particular push-pull is going on. With publishers worried about losing avid YA readers who are “aging out” of the genre, and eager to capture adult readers who have been “reading down,” a new subgenre has been born: new adult. Roughly speaking, these are books geared toward readers 18 to 23, tackling issues of, well, new adulthood. What exactly that means, though, is in flux. And whether retailers will take to the term—which many agents and editors are now regularly using—remains to be seen.

“Even though the term is a relatively new one, the content has always been there in literature and movies,” explained Gina Wachtel, v-p and associate publisher at Random House. Wachtel, who is overseeing a slate of new digital imprints at Random House, among them a new adult one called Flirt, said these books feature characters who are at “the stage of figuring out who you really are—and all that goes with it.”

Talk to editors about new adult and the first thing you will hear is that the term is fluid. While these titles will likely feature 18-year-old to 20-something protagonists, fixating on the age of a character misses the point. Lucia Macro, a v-p and executive editor at William Morrow, said the new adult tag speaks more to voice, style, and theme. Asked if the term was necessary, Macro said it’s useful as a marketing tool. “Whether people want to admit it or not, publishing is a lot about marketing, and when you’re marketing to people it’s necessary to have [the appropriate] terminology.” She then added: “In-house it helps people wrap their brain around a book, especially when you have maybe 10 seconds to explain it to them.”

How long has the term “new adult” existed? The answer depends on who you ask. If you believe the Internet, specifically Wikipedia, the term was coined in 2009, at St. Martin’s Press. Jennifer Weis, an executive editor at SMP, said that tidbit relates to a meeting the publisher had that year with the former-packager-turned-SMP-publisher, Dan Weiss. Weiss pitched a number of books in, Weis recounted, “that mid-adult range.” Looking for a term for these books, Weiss and his then-assistant launched a contest; the winning entry was “new adult.”

While the term has undoubtedly caught on with editors and agents—many say they’ve been hearing about “new adult” books for years, but have only been using the term for about six months—it does not mean much to retailers.

Kenny Brechner, owner of Devaney, Doak & Garrett Booksellers in Farmington, Maine, said he doesn’t think the term will have much appeal to readers. “If there was a great category name that I thought would attract customer interest and generate sales, I would take it on. I’m not going to try and market something I’m reasonably sure will be perceived as lame.”

One of the marketing goals of the term is to catch what editors and agents call the “post-YA reader.” Merrilee Heifetz, an agent at Writers House, who recently sold two books she classified as new adult, said this element is key. “We had this huge boom in the YA market, and now we don’t want to lose those readers. For a teen who was a voracious YA reader [the new adult tag] offers a way to say, here, these books are for you.”

Margo Lipschultz, an editor at Harlequin’s HQN Books, said she thinks there is more going on with the term than marketing, and that the category is filling a hole, especially in the romance genre. Lipschultz said she used to go to the bookstore in college looking for romance titles that also dealt with issues geared to readers her age, but could not find any. Back then, these were titles that “YA bookstore buyers felt were too old for their readers, and adult buyers felt were too young for theirs.” To Lipschultz, that lack of shelf space was one of the main drivers of the boom in the bestselling self-published romances dealing with more adult themes.

Lipschultz thinks a spate of bestselling self-published romance titles that publishers have been acquiring at greater speed and for rising advances could all be classified as new adult. Among them are Jaime McGuire’s Beautiful Disaster (which Atria acquired); Jessica Park’s Flat Out Love (which Amazon Children’s acquired); Sylvia Day’s Reflected In You (which Berkley acquired); and Cora Carmack’s Losing It (which William Morrow acquired). Lipschultz said now it is clear that there is a readership for the books. The question is, what format to publish in.

Another thing the new adult tag does, insiders noted, is signal content that some will consider too mature for teen readers. Since the rule in entertainment has long been that it’s more acceptable to feature violence than sex in content geared at kids, publishers need to have clear terminology when it comes to marketing books that feature sex to young people. “You never want to go to stores and promise [them] something in YA, meaning it doesn’t have explicit sex, and have them get something they are not expecting,” explained Tara Parsons, executive editor at HQN.

Weis, at SMP, thinks the new adult tag also speaks to a certain change afoot in reading habits. Having recently acquired a novel she is categorizing as new adult, Sadie Hayes’s Start-Up (about a brother-sister duo at Stanford launching a tech business), Weis believes you cannot undervalue what publishers saw happening with both Twilight and the Hunger Games: mothers and daughters reading the same book. “We have an avid YA base that is getting older, so we’re trying to figure out how to accommodate that. We also have the parents of that YA group, who are more actively involved in what their children are reading.”

Although most booksellers PW spoke to had not heard the term “new adult,” there are some who are recognizing the growing swath of books that are sort of young adult, but not really.

Emily Grossenbacher, the children’s book buyer and manager at Lemuria in Jackson, Miss., said she has been trying to figure out the best place to put books that she considers “crossover YA.” Currently she is placing these books in her Popular Fiction section, which she considers “a catchall for really great reads.” At the moment, titles in this section range from the Fifty Shades trilogy to various books by YA author John Green. Nonetheless, she does not love this solution. “It’s definitely [an issue] we’ve been thinking about,” she said. “I don’t know if putting the books in YA into new adult is the answer. You’re still going to be asked if new adult is kids, or adult.”