could have been in for a surprise if they visited Highgate Cemetery any time over the past few years. While rese' />

Admirers of The Time Traveler's Wife could have been in for a surprise if they visited Highgate Cemetery any time over the past few years. While researching her second novel Her Fearful Symmetry, which is set in the North London graveyard, Audrey Niffenegger immersed herself in the colourful lives of its famous inhabitants, who include Karl Marx, George Eliot and Douglas Adams. She became such an authority that she began to lead tour parties around its historic grounds, something she occasionally continues to do.

"I would hate for people to show up expecting it to be me," she says cautiously. "I give tours whenever I am in town but that's really random in terms of when that might be. But the other guides are phenomenal, some of them have been doing it for decades and they're so knowledgeable. Most of what I learned about the place has come from them. It's worth going and just about everybody who takes you around has their own unique route."

The Friends of Highgate Cemetery, the volunteer society that runs the graveyard, are fiercely protective, recently berating London Mayor Boris Johnson for listing it as a tourist attraction.

While the Newbury Library in Niffenegger's native Chicago published a pamphlet pinpointing the stairwell where the time-travelling Henry becomes trapped in her bestselling debut, Niffenegger is wary of the extra attention her new offering will inevitably bring. However, from numerous Hammer horrors in the 1970s to Tracy Chevalier's novel Falling Angels, the cemetery has long featured in films and books.

"I'm a bit worried but the Friends of Highgate are really calm," she says. "They say, 'We've coped before.' When Tracy's book came out there was a bump in visitor numbers but they dealt with it."

The 46-year-old planned to base the novel around Graceland cemetery in Chicago before relocating it to London. "It's amazing but not as amazing as Highgate," says Niffenegger, who first approached Friends of Highgate Cemetery chairman Jean Pateman just before the publication in 2003 of The Time Traveler's Wife. "They weren't super-responsive back then and I later discovered that they get hit with media requests day in, day out. At the time when I first said I wanted to use the cemetery in my novel, they laughed at me but since then they've been very obliging."

Pateman may have been swayed by the success of The Time Traveler's Wife, which has sold more than five million copies worldwide. Much is riding on Her Fearful Symmetry, for which Niffenegger reportedly received a hefty US$5 million ($6.9 million) advance. It is arguably this year's most anticipated release after Dan Brown's mega-selling The Lost Symbol. However, despite spending seven years completing the book, Niffenegger is not allowing the pressure to get to her.

"It was daunting at the beginning because it was difficult to collect my attention span," she admits. "The reason it took so long is that I did a lot of travelling around after The Time Traveler's Wife came out. But rather than being out in the world all the time, what I really needed to be doing was sitting in a quiet room writing. But the research was an interesting experience and I spent a lot of time at the cemetery. It was difficult not to do that all the time and to instead sit down and work."

The novel centres around Julia and Valentina Poole, two identical American twins who move to London after their estranged late aunt Elspeth bequeaths them a flat overlooking Highgate Cemetery. However, her spirit remains a presence in the house as she haunts the girls and the apartment block's other motley residents.

The fantasy elements are less pronounced than in The Time Traveler's Wife. Instead of referencing fantastic tales like H.G. Wells' The Time Machine, Niffenegger was inspired by spooky 19th century thrillers like Wilkie Collins' The Woman in White and Henry James' The Turn of the Screw.

"What I wanted to do was to introduce the ghost so quietly that you don't think, 'Holy cow, she's dead!' all the time," she says. "Instead I wanted the reader to get involved in the characters relating to her."

Like The Time Traveler's Wife, Her Fearful Symmetry explores loss although in a very different way. "It's more overt than in some of the other things I've done," she says. "It's one of the primary things that everyone has to go through, whether it be your loved ones going away or death. We're all going to lose people or people will lose us. We can't all vanish at the same time, have the curtain go down and everything end simultaneously."

Niffenegger has declined to see the Eric Bana and Rachel McAdams-starring big screen adaptation of The Time Traveler's Wife, which opened to mixed reviews but topped the box office when it recently opened in Britain and America. But despite sentimentalising the romance and simplifying the nonlinear storyline, the film certainly had female members of the audience in tears when I saw it just after speaking to the author.

"I'm just kind of wishing it well and viewing it from afar," she says. "I didn't have any control and no input. The film-makers really did whatever they wanted to do. It's really their film, something that they did completely unfettered by me."

Niffenegger is concentrating on her next novel The Chinchilla Girl in Exile, which once again delves into the bizarre world of the weird and wonderful. "It's about a 9-year-old girl who has a birth defect where you're covered in hair," she reveals. "In the past, people would have treated her like a circus freak, who would have been attached to some royal court.

"It's about how much our attitudes have changed in the modern world towards people who are different. What would it be like to grow up actually looking quite attractive but in a very different way? It's kind of a coming-of-age novel of my little hairy girl."

Her Fearful Symmetry (Jonathan Cape $38.99).