World Book Day on 2 March marks the 20th anniversary of the event, and the third time I’ve written a Horrid Henry book especially for it. I, like this year’s nine other World Book Day authors, who include Jacqueline Wilson, David Walliams and David Almond, get no royalties for these £1 books, and publishers donate all their costs. So why do it?

I once did an author event in a bookshop, and a child came up to me afterwards. “Are we allowed to touch the books?” he asked. I realised he’d never been inside a bookshop, and this strange environment was as alien to him as stepping into a betting shop would be for me. A book token is a passport: the 15m tokens that will be distributed among all school pupils in the UK and Ireland will enable them to go to any bookshop to choose a free book. For many, this will be their very first book – around 15% of UK children have no books of their own. It’s a shocking and depressing statistic.

I still remember the first time my parents let me choose my own book. I was six years old, in London, and I bought The Pancake, a collection of fairytales with a rough purple cover. I left the shop in a state of bliss, clutching that paperback tightly, marvelling that it was mine.

I believe passionately that books are every child’s birthright. World Book Day exists to encourage children to read for pleasure, and, by letting them choose one of the 10 books, they can follow their own tastes and inclinations.

At a time when our libraries are under threat, opportunities for reading are diminishing. I’m proud to be part of such an important initiative. Parents, treasure those tokens, and enjoy an outing to your local bookshop. And remember, let the kids choose.

• Francesca Simon is author of World Book Day £1 book Horrid Henry: Funny Fact Files.