Millions know him as "the Fonz", the slick-haired, leather-jacketed mechanic whom he played in the hit 1970s sitcom Happy Days.

Now, Henry Winkler is reinventing himself as a best-selling children's author. The 64-year-old American actor has written a set of 17 books featuring a young dyslexic child, Hank Zipzer, which have already sold 2.5 million copies in the US and are now being published in Britain.

"As a seven-year-old, I knew I wanted to be an actor," he says. "But if you want to know what means the most to me, it's the books."

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He and his co-author, Lin Oliver, are about to start working on a new series of children's books called Ghost Buddy, which revolve around a 13-year-old boy with an imaginary best friend. Winkler said he could never have imagined becoming an author when he was a schoolboy, adding that he had not even read a book until he was in his 30s.

"I was in the bottom 3 per cent when I was at school," he said. "I was told I would never achieve. My parents had an affectionate term for me: 'Dummerkind' [dumb kid]. That was really very supportive. I had this teacher called Miss Adolf – I think she was related. I didn't do well at school."

He said his academic failure led him to have a lot of "negative thoughts" and that he worried he would never be able to find a girlfriend – something his character in Happy Days seldom had to worry about – or a job.

It was not until much later that Winkler realised he was dyslexic, and he describes his books as an attempt to find comedy in a dyslexic world. "Because you're not good at academics, it doesn't mean anything. You can still fly like an eagle when you discover what you are good at," he said. "Everyone has a talent inside them – you just have to find out what it is."

The character Hank is based on a boyish Winkler and gets into the same kind of scrapes he can remember from his school days. In one book he is supposed to write about Niagara Falls, but as he cannot write he decides to build his own version in the classroom – which then floods because it is made out of cardboard. The book's title is Niagara Falls – Or Does It?

Winkler survived school to gain a master's degree at Yale College of Drama, where he remembers a fellow student called Alvin who bullied him. "Alvin was always questioning why I was getting parts. He was always saying 'I'm a better actor than you'."

He did not realise he was dyslexic until after his son Jed was diagnosed with the condition. "I realised – that's me, too," he said. "The first novel I read was when I was in my 30s. It was a triumph – all of those words in those covers." Now, he solemnly puts every book he finishes reading on a set of shelves at his home to remind him of what he has achieved.

Realising he had dyslexia also explained why he had experienced such difficulties in reading his scripts. "I can't read in front of a group, so when I got a copy of the script of Happy Days, I'd memorise it later," he said. If he was asked to read his lines before he had been able to learn them by heart, he would make a stab at it and make the excuse – in typical Fonz style – that he was just giving the director "a flavour of it".

"I can't do Shakespeare," he added. "I went to the Royal Shakespeare Company and saw them all reading it as if it was their personal conversations and I just thought, 'Well, I'll leave it to them'."

However, he said he had done his bit for improving the take-up of reading in the US by something his character said in an episode of Happy Days.

"The Fonz said to Ricky [his friend]: 'You should register at the library – you can meet chicks there'," he said. "The following week registration for library cards went up by 500 per cent."

Winkler is currently in the UK on a whistle-stop tour of schools promoting the My Way campaign, which aims to persuade children that there is no such thing as being stupid, just different approaches to learning.

By the end of this week, he will have visited 60 schools. During his time in the UK – he regularly returns to take roles in pantomimes over Christmas – he has also become involved with the UK Teaching Awards, after a chance encounter at a theatre in Croydon while he was playing the character of Captain Hook in Peter Pan. He met the theatre manager's sister who had just won the Primary Teacher of the Year Award, which persuaded him to take part in an auction on Absolute Radio last year where celebrities had to convince listeners to vote for their charity.

"I got up at 3am in Los Angeles to do a live broadcast," he said. This led to £40,000 of sponsors' money being handed to the Teaching Awards. As a result, the Henry Winkler Teaching Award for Special Needs has been established, which gives three £10,000 bursaries for projects in UK schools. The outright winner will receive an extra £15,000 at the awards ceremony in October.

Despite his re-invention as an author of children's books, Winkler has not given up on acting. He can currently be seen starring in a new TV series called Royal Pain, where he plays an anguished dad, and plans to return to the US to take part in another programme called Children's Hospital, playing a hospital administrator.