It's not surprising that there's an action movie at the top of the box office this weekend.

What is surprising is the kind of action movie. It's called The Hunger Games and in some ways, with its spaceships and explosions, it's typical of what Hollywood does all the time. But in other ways, it is an entirely new kind of film and part of a much bigger sexual, social and cultural shift affecting not only movies and books but millions of young women around the world.

Lorna Drummond (pictured below right) has already been to see The Hunger Games and loved it. She's been racing through the trilogy of books by Suzanne Collins on which the film is based and is a big fan of the central character, Katniss Everdeen. Katniss doesn't go google-eyed over guys, says Drummond. She doesn't take any nonsense. She's strong , confident and willing to use violence when she needs to.

And she needs to. The Hunger Games is set in a future dystopian America ruled by brutal overlords who force their young people to fight each other in a televised gladiatorial contest until only one is left alive. Some of the violence in the 12a film has attracted criticism but Drummond thinks that's misplaced. Yes, there's violence, but in most ways Katniss is just an ordinary 16-year-old girl trying to protect her family and friends. Drummond gets it.

And so do millions of other young women. The Hunger Games trilogy of books have been best-sellers that tap into the same audience that loved the Twilight franchise, featuring Bella and her vampire lover Edward, and before that Harry Potter with the strong-willed wizard Hermione. Until recently, this was an audience that no one really knew existed, but now publishers and movie-makers have realised girls and young women also love fantasy and escapism. Wizards and vampires and futuristic gladiators are not just for boys. Girls can be geeks too.

Lorna Drummond thinks this represents a big and welcome change in popular culture. The 27-year-old started reading Harry Potter in her teens before moving on to Twilight but says when she was a young girl all the role models in the fantasy books and films she liked were male.

"That was just the way things were," she says. "When I was really young, there was Sweet Valley High and things like that but they were all twee and nothing really happened – there was no action, there was nothing exciting. I think it is about realising that not all girls want to read about My Little Pony and hair and make-up. Maybe girls do want action stories as well."

But it's not just action they want. For women, there has to be a strong emotional content, which is why the Twilight stories were so popular with girls and young women aged from 15 into their twenties. The formula is romance plus action, the conventional plus the unconventional, and millions of women have embraced it.

Film critic Mark Cousins thinks the big studios finally understand this, and says films for this audience are long overdue. "The teenage female imagination is both exciting and conventional," says Cousins, "that's why the films are edgy but also, in a way, coy. The best films I've seen recently have been about teenage girls: Margaret, Hunger Games, Martha Mary - and that's good. Now all we need is for film-makers to follow such characters into adulthood and old age and we will have corrected the stupid male focus in mainstream cinema that has existed since the Victorian era."

Cousin thinks it will take Hollywood a while to get it right, however. "Hollywood has been playing an interestingly quasi-feminist game in the last decade or so," he says. "It has made its action heroes and stories more female but they have felt cross-dressed in some ways. Angelina Jolie kicking ass is a bit like a male protagonist that you can fancy. These new films aren't cross-dressed."

What's happening now, says Cousins, is exactly what Lorna Drummond describes: a move in the action movie/science fiction genre away from the male domination of the past. "Roger Corman said that when writing action and sci-fi movies, that there should always be 'the hero and the girl'," says Cousins. "Now there is the hero and the boy. I think that The Hunger Games is a great piece of teenage art. Bring it on."

The publishers and film studios are bringing it on. In fact, after the success of Twilight and The Hunger Games, they are desperate to find the next idea in the genre. Suddenly, there is a young female market that is willing to pay for books and films and merchandise and everyone wants to be part of it. Josie Freedman, co-head of the book-to-films department at the talent agency International Creative Management, said recently that every single studio wants to capitalise on the young-adult franchise. "It's what's selling on the publishing side and on the film side," he said.

Publisher Jo Fletcher, who has her own fantasy imprint at Quercus, says the expansion in fantasy for young-adult women is the latest in a number of crazes to grip publishing and film-making.

"In publishing and in films you get 'crushes' when there is one thing that everyone wants to read – for a while, it was paranormal romance, then it was chick-lit, then in the mid 80s it was horror. In children's books you get the same thing – first, it was Harry Potter. So you always get little pockets of excitement about one thing or the other."

Fletcher traces the beginning of the latest crush to Harry Potter. "Those readers grew up over seven books," she says. "They might have been 11 or 12 when they started but by the time they finished they were in their early 20s and they are looking around for something else like that to read. And then Twilight came alone."

The result, says Fletcher, has been positive for young women readers looking for something exciting but also engaging. "For a long time, the geeky thing was male but girls can be geeks too. The research has shown that the demographic for the great rise in cross-over material such as Twilight was young women aged between 16 and 24. The need for romance in young women has always been gigantic and if you happen to like fantasy as well then why wouldn't you go for books like these?"

This has certainly been the appeal for Lorna Drummond. She – and Fletcher and Cousins too – believe there is a kind of equalisation going on. They don't think that after years of every book and film being about boys and men, every book and film should lead with a woman. But what they do see is the beginnings of a re-balancing to put real women, as well as real men, at the centre of one of the biggest and most popular genres in the world.

But what about the influence that the movies are having on young women? Drummond says every one of her female friends in their twenties has read the Twilight books and she has noticed their effect.

"There's definitely a lot more EMO and slightly gothy girls kicking about," she says. "The books had an influence on that – you could look on Amazon and see all the eyeliner and Twilight jewellery for sale. Teenage girls will inevitably be looking for something to follow and it's likely to come from films or music or TV."

Drummond has concerns about the central message of Twilight (girl gives up everything to be with a man) but says The Hunger Games, in which a girl fights to protect her family, is much more positive. And both the franchises, she says, have a positive legacy to pass on to young women – there has been big social change in the female population and now books and movies are reflecting that.

"I look at my mum's generation," says Drummond, "and you only ever moved out of home when you got married and that was you set up for life and you'd have kids and housework. There's been a massive shift. There's more freedom to do things. There's more adventure."