Stieg Larssons' Millennium Trilogy books sold 18 million copies — a phenomenon by any account. And much of that success can be attributed to the series' popularity with women, says Claude Brodessor-Akner at New York, who points out that 71 percent of the fans of The Girl With the Dragon Tattoo's Facebook page are female. Yet, early tracking for David Fincher's upcoming film adaptation suggests that the movie's PR is alienating this fan base, with only 36 percent of women between the ages of 25 and 79 expressing "definite interest" in seeing it. The movie's producers are going so far as to move up its release date one day to Dec. 20, hoping to build positive word-of-mouth sooner vs. later. What's behind women's reluctance to embrace the film? Here, four theories:

1. The story is too violent
Larsson's books brutally depict violence against women, but reading those scenes is one thing, and seeing them on the big screen is another, says Brodessor-Akner. While women go see slasher movies and horror films, those movies have a layer of fantasy that insulates the viewer from the action. "Hyper-realistic violence against women," like the kind in Dragon Tattoo, "is very different from the average horror movie," one marketing executive tells New York. "They're escapist, 'movie-date' oriented." Women who've read the book know that there's nothing escapist about the violence in Dragon Tattoo, and may be disinclined to subject themselves to it on film.

2. The marketing is scaring them away
The unflinchingly dark and gritty trailers and other marketing materials have been very up-front about the film's brutality and have done nothing to overcome women's resistance, says Brodessor-Akner. "I am not surprised that women don't want to see an ultra-violent movie about women being tortured and raped," another marketing insider tells New York. "Women see these trailers and are being scared shitless away from it." Part of that may be Fincher's fault, too. The director has a hand in all of the marketing, and has refused to pare down its content.

3. The books' target age group aren't typical moviegoers
There's a big difference between carving out time to read a book alone, as millions of women did with Dragon Tattoo, and going to see a two-hour movie full of "horror and depression," says Katey Rich at Cinema Blend. Women over age 25, the target demographic of the Millennium Trilogy, are likely to have children and commitments — meaning they'd have to hire babysitters and rearrange schedules to make time to see the film, as opposed to reading 20 pages of the book before bed.

4. There's a lot of competition
The film's poor tracking with women may have more to do with simple math, says Joshua L. Weinstein at The Wrap. A glut of films are getting Christmas releases, and they're siphoning attention away from Dragon Tattoo. Dec. 21, the film's original release date, is the same day family-friendly, mass appealing movies such as The Adventures of Tintin, We Bought a Zoo, and Mission: Impossible — Ghost Proctocol have their wide releases. Four days later, the epic weepie War Horse hits theaters. By bumping Dragon Tattoo up a day to Dec. 20, the film has a chance to "beat the Yule crush."