The idea of a total stranger leafing through your diary would mortify most teenagers. Having left behind those angst-ridden years some time ago, however, Jacqueline Wilson is ready to lift the lid on her adolescent hopes and fears. A hormonally-charged mix of diary extracts, stories written at the time and memories of the past, Wilson’s latest book – like all her others – doesn’t shy away from real issues.

First love, problems at school, friendships, her parents’ troubled relationship, not to mention the difficulties encountered trying to maintain a beehive hairdo: My Secret Diary covers them all. Styles may change but the woes of the average teenager remain remarkably constant, which Wilson hopes will give her memoir a broad appeal. ‘I get a lot of letters from girls in their early teens fussing about not having a boyfriend and worrying about their parents splitting up,’ she says. ‘So I thought it might be interesting for them to see that I was just as stroppy and silly as any other teenage girl. And also that it might be good fun for anybody around my age who wanted to reminisce about the 1960s, because life has changed enormously in so many ways.’

Wilson may have spent her youth in the 60s, but the majority of her characters live in the here and now. Capturing the way they feel about life has always been Wilson’s major strength, a skill heightened by her penchant for writing in the first person. But as she says, life has changed and continues to evolve at a breakneck speed. The technology of her teens has been replaced by iPods, Wiis and countless other bits of machinery that use the alphabet in unorthodox ways. Has Wilson ever felt pressured to reflect that in her novels?

‘No, I’ve totally given up any attempt to keep up with modern technology because I’m automatically going to get it wrong,’ she says. ‘And I try not to have current slang in my books or a craze that people are dotty about for six months and then go off. But I do think it would be wonderful if there was a master copy of each of my books and every now and then – like when poor old Woolworths went – it would automatically pick up on that and insert a substitute. Sadly, that’s not a possibility.’

Wilson also points out that the vast majority of her characters are probably too poor to own an iPhone or Nintendo DS, most of them having been born, or thrown, into a hard-luck story. Over the years, Wilson has tackled some fairly controversial subject matters, winning herself both praise and criticism in the process. In the course of almost 100 books, we’ve had bereavement (Double Act), adoption (Dustbin Baby), divorce (Clean Break), bullying (Bad Girls), single parents (The Illustrated Mum) and home repossession (The Bed and Breakfast Star).

Contrary to how it may seem, however, Wilson doesn’t wake up in the morning and hatch elaborate new ways to shock young readers. ‘I know people think I almost take delight in covering controversial subjects, but I think more about what I want to do artistically and what I feel is best for the plot of the book. After my first draft I go back and think, “now is this scene going to worry any child enormously?” I try hard to take things almost to the edge of where you can go, but not that one step further. It’s so difficult, because you can’t please everybody.’

She must be doing something right, though, because book sales of over 20 million don’t lie. Nor does the honour of being the most borrowed author in British libraries four years running. The former may have made Wilson ‘very comfortably off’, as she puts it, but in some ways the latter is closer to her heart. ‘That meant a great deal to me because I was in the library practically every other day as a child. And the fact that lots of children are clearly using libraries, and growing up with a really good reading habit is great.

At the age of 64, Wilson does a remarkable job of speaking with a voice 50 years her junior. Whether she’s writing as the feisty, looked-after child Tracy Beaker, flamboyant ghost Vicky Angel or any of her myriad characters, Wilson strives to make them as believable as possible. How difficult is it to step inside the mind of a child, and a particularly troubled one at that? ‘I don’t know what it says about me,’ laughs Wilson, ‘but I find it surprisingly easy. I don’t really know how I do it, I just suddenly become them, like an actress taking on a role. For the most part I find it much easier to write as a child.’

As writing careers go, Wilson’s is highly covetable. Aside from the enviable books sales and copious awards, she spent two years as Children’s Laureate, received an OBE and, in 2008, became a Dame (a title she is ‘thrilled to bits about’ but doesn’t demand to be called). Her forthcoming appearance at the Book Festival will sell out (again) and yet more adaptations of her books are planned for both stage and small screen. Jacqueline Wilson may have spent her entire working life writing, but somewhat inevitably it comes at a price. ‘It has been fantastic but you never quite get to the point when you can just concentrate on the sort of writing you want to do most. For many years I had to do all sorts of other commercial work simply to pay the bills. Now, thank goodness, my books do make money, but with that success comes charity work, committees, many fan letters; so I still struggle to find enough hours in the day. But if it didn’t happen, I’d probably be the first to complain.’

Jacqueline Wilson, Charlotte Square Gardens, 0845 373 5888, 23 Aug, 10am, £4.