Interviewing Mathilde Madden is rather an odd experience for both of us, I think. To me she's Tilly, mother of Coco and Boris. We meet up at pre-school and coffee mornings and our children sometimes play together. But her alter ego, Mathilde Madden, writes kinky, erotic fiction for the imprint Black Lace Books - this is what feels weird. How often do you talk about your friend's fetish fantasies over tea and digestive biscuits? Not only is the tape rolling, but It all feels deeply un-British. So it's just as well that there's a lot more to talk about than just the sex.

Mathilde has written three books. Her first, Peep Show, dealt with voyeurism, the second, Mad About The Boy, with a woman who wanted to pay for sex. Her most recent, Equal Opportunities, is about David, who thinks his love-life is over after a car accident leaves him in a wheelchair and Mary, who finds his helpless state a real turn-on. They meet at a library and within hours are having a hot and heavy relationship, with Mary very much the aggressor.

Written in the first person, from both characters' perspectives, this is not an easy book to read, as it goes into some dark areas. Mary's sadomasochistic predilections often seem cruel, yet David is with her all the way. His legs may not work, but he is no victim. Throughout the book, you see how, while he struggles with his obsession for Mary and the nature of her obsession for him, she has helped him immeasurably to move forward with acceptance of his disability. Mary is not an easy character to like, but, because of the way David feels about her, you end up admiring her.

Mathilde got the idea from a TV soap. "One of the characters had a car accident and ended up in a wheelchair. He thought no one would want him anymore and I was thinking, 'I don't see why that's an issue'."

Initially she wrote a short story, but decided there was enough meat to write a novel. For research, she interviewed Mik Scarlett, who campaigns for disabled people's sexual rights. "He was really useful, because he gave me that inside information, especially things like the right kind of slang. He also just explained practical things to me, like how to get a wheelchair into a car," she said.

So what was it about this particular issue that Mathilde found so interesting?

"I really wanted to talk about the whole nature of why people are attracted to the people they're attracted to and why people fall in love with the people that they fall in love with," she said. "One of the reasons that Mary loves David is because he's disabled, because physical attraction is about physicality and disability is about physicality as well. How she deals with those feelings in the book ends up being central - her own feelings about whether or not it's ok to be attracted to him, because he's disabled."

Erotic fiction is not generally something that people admit to reading, let alone writing. What reaction does she get when she tells people what she does?

"I've never had anyone express disapproval to my face. It is just fiction. If people don't like it, they don't have to read it. A lot of books that you buy in bookshops have explicit sexual scenes in them and no one seems to think that's a bad thing. It's just part of life."

While Black Lace is being rebranded as romance, Mathilde's books deal with very adult themes. I asked why she was interested in topics like voyeurism. "I don't want to write about things that have been done before and I want to write about female characters who are quite sexually obsessive, because I think obsessive people are more interesting," she said. "All my books are about women who have fetishes. I think that's something that hasn't really been written about very much."

Mathilde, who used to live in Brighton, where she was a stand-up comic, honed her craft by writing online fan fiction, writing stories about characters in TV shows and books, including Buffy the Vampire Slayer, Battlestar Galactica and Angel.

She began writing for Black Lace after reading in a magazine that they were looking for contributors. She also writes for science-fiction whodunnit website Perplex City, and is now writing the first of a paranormal romance trilogy involving a werewolf and female werewolf hunter for Black Lace. A huge genre in the US, it originally developed as an ebook phenomenon.

Mathilde also eventually hopes to get published as a crime writer and is finishing a thriller. Given all her other commitments, I don't know how she finds the time.

Equal Opportunities is published by Black Lace at £7.99.