The author Anthony Horowitz was just 23 when his first children's novel was published - in 1979.
Horowitz: gets his children to rule on what's cool
But, he didn't hit his stride until he returned to the fantasy he developed as a bored schoolboy: that he was really a teenage spy.
His series of novels about Alex Rider, a reluctant teenage recruit to MI6, has proved immensely popular, with girls as well as boys.
The sixth, Ark Angel, has just been published.
Anthony Horowitz came in to the Breakfast studio, to tell us more.
Fourteen year old Alex Rider made his debut in the novel Stormbreaker.
He's MI6's secret weapon - an ordinary teenager armed with James Bond gadgets, from a customised mountain bike to explosive spot cream.
Sales of the Alex Rider books have now topped the two million mark.
Anthony Horowitz is a prolific author. He's also written the Diamond Brothers trilogy for children - and the wartime detective TV series Foyle's War for ITV.
Ark Angel by Anthony Horowitz is published by Walker Books. ISBN 0-7445-8324-1
A film production company, Samuelson productions is currently looking for boys from 12-14 who could play Alex Rider. For more information, see Walker Books' website