The vampires that sank their fangs into Harry Potter were born in the low desert of Arizona. They arrived in a dream, were immediately translated to paper, spread through the adolescent population like a virus and transmogrified into a publishing phenomenon.

The trail to their origin leads north out of Phoenix. Under pain of a slow death, it has been agreed that an exact location will not be mentioned. If the truth got out, the place would be overrun with besotted teenage bloodsuckers. Let us just say that off a highway, down a dirt road, lies an adobe-style house, secluded among giant Saguaro cacti, their arms pointing wildly in every direction like signposts striving to send a visitor the wrong way. This is the home of Stephenie Meyer, a Mormon mother of three who has sold seven million copies of her books about high-school vampires and is building the most convincing claim to date to be the true heir to the world's most successful author.

Last year, when the third book in Meyer's series was published just two and a half weeks after Harry Potter and the Deathly Hallows hit bookshops, it went straight to No1 in American charts; a high school displacing Hogwarts to depose the final instalment of the Potter saga. “The next J.K. Rowling?” asked Time magazine recently, before appearing to answer its own question by including Meyer in its list of the 100 most influential people in the world.

Never heard of her? Well that's probably because you are not 13 and female. But you soon will. Although five million of her sales have been in the US, momentum is growing in Europe and with the release of a film of Twilight, the first book, scheduled for early next year, the books are expected to take off here. British bookshops are planning midnight openings on the day that the fourth book in the series is published in August.

On the face of it, the formula for Meyer's fantasy series sounds unlikely. These are vampire novels with little blood shed and a strong moral message, written by a woman with a robust Mormon faith who does not like horror books (she hasn't even read Dracula) and has never seen an R-rated film on principle.

The books are essentially high-school romances with a twist. The protagonist is an ordinary pupil called Bella, who falls for Edward, the best-looking guy in the class. The twist is that he happens to be a vampire and, while he is very taken with her, too, he has to watch out that he doesn't get carried away and have her for lunch. How their relationship develops in these awkward circumstances and how the heroine deals with other less scrupulous blood-guzzlers, is the basis of the books. There is dark stuff lurking off stage but it is not explicitly presented to the reader.

Meyer, 34, had no plans to become a writer. She studied English at Brigham Young University, a college run by The Church of Jesus Christ of Latter-day Saints in Utah, but her only professional work before she started a family was as a receptionist in a property company. Then one night in June 2003 she had a dream. She prefaces this story by saying: “It's absolutely true and sounds so cheesy. I was really embarrassed about telling it at first. My publicist said, ‘It's a good story'. I'm like, ‘It sounds silly: no one is going to believe it'.”

In her dream Edward and Bella were standing in a meadow having a conversation. “I already knew he was a vampire and he was sparkly and beautiful and she was just kind of ordinary and in awe of this creature. He was explaining how hard it was not to kill her and she was amazed that he wanted to be around her even if it was risking her life.” When Meyer woke up she wondered: “Where would it go next? Would he kill her or would they work it out? I just thought about it until I had to make breakfast.”

Later that day she wrote down the dream and kept writing. “The dream is what started me off. I had fun that day. It was just ten pages. I didn't think about writing it as a book, I just wanted to see what happened next. I know when I started writing because I had it marked on my calendar. That was the day I started my summer diet and it was the first day of swimming lessons for the kids.”

She felt compelled to keep writing, oftenwith the youngest of her three sons, who was then a baby, clinging to her. Her husband became “kind of mad at me. He said: ‘You never sleep, you don't talk to me, I never get to use the computer. What are you doing?' I told him I was writing some stuff for fun.”

When she had finished the story, which ran to 130,000 words, her sister persuaded her to send it to literary agents. Of 15 letters she wrote, five went unanswered, nine brought rejections and the last was a positive response from an intern at Writers House, who pretended to be an agent, asked to see some chapters and eventually brought the manuscript to one of her bosses. Quickly, she had secured a $750,000 three-book deal.

Twilight was published in 2005 and two sequels followed at yearly intervals. The phenomenal success came largely from teenagers spreading the news on social networking sites. Then adults - especially mothers wanting to find out what their kids were up to - began to buy as well.

She is well aware of the debt she owes J.K.Rowling. “I'm a big fan. All of us YA [young adult] writers are, especially those of us who write big books. If it weren't for her, our books wouldn't even have gotten a chance. People wouldn't put an 800-page YA book on the shelf because there was no way kids were going to read it. Now everyone knows that kids love big books, you just have to make them interesting for them.”

When her third book, Eclipse, was scheduled for publication so soon after Deathly Hallows, she “pitched a huge fit with my publisher because I did not want my book to come out so close to hers. I saw a tidal wave of Harry Potter that would erase Eclipse. They said ‘trust us'. I thought that the book would disappear.” She remains astonished that she knocked Potter off the top spot. “I still can't totally believe it. It seems kind of... sometimes life does seem like fantasy.”

She is wary of media attempts to draw similarities between her and Rowling. “She has a better Cinderella story than me. She was really down on her luck and then it went crazy in the other direction, but I was in a pretty good place. The biggest similarity between us is our fans, because every fan is also a J.K.Rowling fan.”

Strip away the vampires and it is easy to see how the themes of Meyer's books appeal to teenagers, especially girls. The heroine is swept off her feet by a handsome hero. In the unremarkable Bella, who wins the heart of the charismatic man with a dark secret, there is a strong flavour of Jane Eyre. But the traditional theme of the girl who falls for a monster is also strong. Meyer says that criticism of her as anti-feminist is “a bunch of crap. If anything I am anti-human,” she cracks.

Meyer says she didn't set out to write young adult novels, but just naturally set her story at a high school “because it's the first time you fall in love, it's the first time you kiss somebody. All those feelings are so much stronger. You are not calloused up yet, you haven't had your heart broken a few times so you know how to handle it. Everything is very vivid so it's a lot of fun to write about.”

There is no pre-marital sex in Meyer's books but sex - or the lack of it - is much of what they are about. The pages swim with teenage hormones. Edward's battle to restrain himself from sinking his canines into Bella's neck is an obvious metaphor for the importance of sexual abstinence.

That is hardly surprising perhaps from a Mormon who attended a college where pre-marital sex is a violation of the college honour code. “My high school, college experience, a lot of it was about restraint.” She is appalled by the sexual promiscuity of many teenagers. “As a mother of three boys I just think that there are so many ways you can screw up your life when you are too young to understand what you are doing. I would hope my sons are smart enough to see that coming and make the right choices, so they don't get themselves in a situation where their future is on the line. It makes me sad. I see so many teenagers who have so much promise and they screw it up. Kids don't get to be young any more, it kills me. It's good to be a kid for a while.”

She has known her husband since childhood, but “we didn't like each other at all. He was part of a different crowd and some of his friends were kind of mean”. They ran into each other again when she was home from college and he had returned from a mission with the church of LDS to Chile. They were married within nine months of getting reacquainted and she had not yet finished college. He became an auditor, but has now retired to look after the boys, aged 10, 7 and 6, while she earns millions tapping out her books at a marble desk in the family living area.

Meyer, who does not drink alcohol or caffeine because her church teaches that such drugs can interfere with her ability to express free will, writes books that convey a message about the importance of making careful choices in life. As well as the lack of pre-marital sex, drugs and underage drinking also do not feature.

Meyer believes that this lack of social realism is part of the appeal to her fans. “There are a lot of kinds of reality. There is a lot of representation [in contemporary literature] for a kid in high school who is drinking and sexually active. There are a hundred books they can relate to. When I was in high school, the people I related to were Jane Eyre and Elizabeth Bennett because I wasn't having that experience. I know a lot of kids who relate to my books because they don't drink and they are not sexually active. There are a ton of them but they don't get a lot of representation in literature or television or movies. Kids who are just good kids and follow the rules - they are out there and they don't get any playtime.”

Now those fans have built numerous Stephenie Meyer websites and turn up in droves to events celebrating her characters' birthdays. The internet is awash with teenage scribblings involving the characters from the books, something Meyer has mixed feelings about: “Teenagers are prone to want to live in things they are excited about. I do worry about some of the fiction writers because some of them are very talented and I don't like them wasting their time on something they can never claim as their own.”

She says that some people are surprised that a Mormon is writing vampire novels, but they generally haven't read her. “When you think about vampire novels, there is a lot of gruesomeness, a lot of sexuality, a lot of darkness, blood obsession. When you read my books it is completely different. Really, the whole vampirism thing is a metaphor for feeling trapped in a certain role. I never got into any trouble from the Latter Day Saints people. My strongest fan base is probably in Utah.” How Meyer came to write about vampires, however, is a mystery to her, given that she was very far from steeped in the vampire tradition. She is too “chicken” to read horror and doesn't watch R-rated films because “there are things that you don't need to have in your head. There are R-rated movies that I would like to go and see - I heard The 40-Year-Old Virgin was hysterical. But when you have an unbroken streak, you don't want to mess that up.”

The film of Twilight, the first book in her vampire series, will star Robert Pattinson, who was Cedric Diggory in Harry Potter and the Goblet of Fire and Kristen Stewart, whose films include Panic Room and Into the Wild. It will not be a gore-fest. “I put in a clause in the contract that the movie had to be PG-13 so I could go see it,” says Meyer.

There will probably be more films, and possibly more vampire novels, although the fourth book will be the last written from the perspective of Bella. Meyer's adult sci-fi novel, Host, is published this month.

Despite her prodigious output and huge sales, she scoffs at suggestions that she is turning into the first post-Potter phenomenon. “Everyone is looking for the next J.K. Rowling. It's not going to happen. That's just something that is never going to happen again. She was, is, something that will not be repeated.”

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