Jacqueline Wilson has sold more than 20 million children's books. She tells Freetime her secret of enthralling young people.

Although some of your books are for younger and some for older readers, your main reader-base is the eight to 12s. What is it about that age-group which interests you especially? Jacqueline Wilson: I think that age is a very intense time of your life. You feel as passionately as adults do and you're seeing the world with fresh eyes but you're still your own self. By the time you get to 14 or 15, you're more inclined to want to be adopted by a group, to worry about what people think of you, if you've got a boyfriend or girlfriend etc.

It's interesting, I often can't remember what I did last year but I have almost total recall of what I did and what I felt at that age - the feelings were so intense.

Having said that, I try not to look backwards because it's now so different from when I was that age.

When I was 12, I was left by myself during the holidays while my mother was at work and I was trusted to go to London on the train on my own. I walked to school on my own from the age of seven. It was accepted you could look after yourself - now we look on 12 year-olds as younger and needing protection.

On the other hand, 12-year-olds dress like adults and they know far more about the ways of the world. Adults will often talk to children about problems, even including plans for divorce, whereas in the past you might have known, but only because you heard raised voices in the night.

Do you have a clear picture of who you're writing for? JW: At the beginning, at the first draft stage, it's just for me - I want to get absorbed in my imaginary world. Later, when I type it into the computer, then I'm in a different mood and then I do think about the audience: "This language here is too adult, they won't like that long descriptive passage". But I think you have to go with the flow at first.

I've written about 80 books now and been very lucky to be successful, so you'd think I'd feel more confident, but I don't. With each book, I still worry whether this time I can pull it off.

What you do get, with experience, is the confidence to go on, just keep going and see what you end up with.

You usually write two books a year (I think). How far ahead do you have an idea for a book? Are the next three or four bubbling away? Or just one or two? JW: I've finished the one which is due out in October this year and I'm on about chapter five of the one due out March 2006. The one scheduled for October 2006 is just a sentence or two in the back of a notebook. I like to have a couple of ideas on the backburner all the time. Obviously I concentrate on the next book but I do like to have some idea of what's going to follow.

How do you write? Do you always work at the same time of day, or in the same place? JW: Because I lead a crazy life, with lots of travelling to book-signings and other events, I like to write in notebooks. I write on trains a lot and, if I take some travel sickness tablets, I can write in the back of cars. When I'm on the first draft of a book, I only write for an hour or two a day but when I'm at the computer stage, I do a much more steady four hours a day.

In Midnight, Casper Dream is a very popular illustrator - and you're a very popular author. But he's reclusive, and you're not. Where did you create him from? JW: When I started thinking about Midnight, I knew I wanted to explore a relationship between brother and a sister which was rather strange, almost on the edge of being a bit creepy.

And then I saw a shop in Boston which sells (for adults) fairy books, fairy ornaments, all sorts of fascinating things. It's run by a very poetic kind of man, who seems rather elfin himself. I imagined a set of highly collectable picture books and started thinking about who might create these ethereal illustrations.

And because they're so beautiful, so ethereal, I found myself thinking of this large lumpy man who hides himself away - and he became Casper Dream. I think also that, if a writer's hidden away, his readers can romanticise about him.

You're far from reclusive but are you like Casper Dream at all? JW: As an adult, I'm socially, very out there but as a child, I was very happy to be a solitary child, writing in my room. In my next book, there's a writer who is more like me - the central character, Em, is a great fan of hers. But then, Em also collects Casper Dream's books!

Vicky Ireland has now adapted and directed three of your books. How does it feel to hand your work over to someone else? Do you mind losing control? Does it feel like the same piece of work or something new? JW: It's a huge treat. The first time (The Lottie Project), I did get a bit anxious - although you haven't been part of the process, it is your book and your name is there. But since then, I've got to know Vicky and I know she knows what she's doing. She respects the books and always gets the essence of them but she brings new elements, adds extra dimensions.

I'm sure if I had closer involvement with the process, I'd share all the worry but as it is, I just very happily go along to see the play and it's a delightful experience. It's not scary any more. I do feel a bit of a fraud if I'm watching the show and people come up and say "well done" after all, I didn't create what they've just seen.

What did you read when you were the age of your readers? And what do you read now? JW: Noel Streatfield, because she wrote about realistic children. Little Women, What Katy Did were all favouries. When I was 11, I do remember reading Dodie Smith's I Capture The Castle -about a girl who keeps a diary - she is romantically poor but living in a castle!

Do you write diaries? JW: I start the year thinking I will, just to help me remember the year - but because I write so much with the books and letters to people, by mid-January I've given up. I think as well that, because I write so much for publication, it's very difficult to write for myself, to really let go.

What are you reading now? JW: I like Alison Lurie's books and Ann Tyler's books about odd, quirky, maybe dysfunctional families. I do read a lot of children's books but it's difficult to read them in a very relaxed way because I find I'm always evaluating, thinking about how it's been done. But a lot of my friends also write for children so I read their books and I'm sometimes asked to judge competitions - and anyway, I do have to keep up.