In Harry Potter week, CHRIS TITLEY finds out why JK Rowling's magical books are devoured by children and adults alike.

HE has the whole world under his spell. Some facts and figures to prove it: the Harry Potter books have sold 100 million worldwide. Only the Bible has been translated into more languages.

A staggering 97 per cent of people are familiar with the Harry Potter character, according to a survey carried out by Waterstone's. This also revealed the young wizard's popularity among those who have long left school. Nearly half of adults have either read a Harry Potter book or intend to read one in the next 12 months.

Exactly how did Harry come to grip the nation's eyeballs? The best way to find out is to ask. We spoke to two aficionados, one still at school, one not, about why the wand-waver is wonderful.

Ten-year-old Katie Cross is unabashed in her admiration for Master Potter and co: "I love them. I can't get enough of them."

It took a little time for her affection for the books to grow, she says. "I got some birthday money and decided to get some Harry Potter books because everyone was getting them. I'm a really big fan of reading.

"I got them when I was about seven. At first they were a bit hard for me, but about two years ago I started getting really into them."

When it comes to explaining why the books are so great, Katie, from Moss Street, York, almost doesn't know where to start.

"As soon as I picked up the book, I felt I was in the story. I am one of the characters. I haven't read another book that describes so much wizardry. It's amazing how JK Rowling has written the book. Harry Potter is a brilliant character."

She also identifies with Harry's progress in lessons at Hogwarts. "He's just a normal child but he's not going to a normal school where you do maths and English. He's going to a school where you do spells and potions."

But Katie, who goes to Upper Poppleton Primary School, says that stories of friendship and bullies, nice teachers and scary teachers, make Hogwarts a recognisable place. "There are people who don't like Harry like there are in every school. Someone dislikes someone else everywhere."

Katie admits she is not the only fan in her household. "My dad has read virtually all my books. As soon as I get them, my dad's read them."

Which neatly brings us to the astonishing appeal of Harry Potter to adults.

Philippa Morris, 31, co-runs the Little Apple Bookshop on High Petergate, York. She has read all four books and discussed them with friends and customers.

Before Pottermania took off, she was aware that the books were out of the ordinary.

"From very early on, I had friends who were reading the first one, who came out and said, 'this is great, this is great!'

"You kind of knew it was something special by the time Chamber Of Secrets, the second one, came out. It's unusual in bookselling to sell a lot of hardback children's books. So when people were advance ordering the second one you were thinking, 'this is interesting'."

She finally decided to read them for herself, and instantly understood their attraction.

"They're brilliant escapism. As adults, they take you back to your childhood and the excitement of reading.

"There's something really good about getting to know the characters through a sequence of books, and developing a familiarity with the place.

"You are introduced to Hogwarts, the wizard school, in the first book. By number four you feel you can run around it with Harry because you have been down that corridor and across the lake before."

Many children can identify with one or other of the other characters, she believes. "Because Harry's an orphan, he has to deal all the time with this loss. Ron, though, has to deal with living in a big family and all the pitfalls that entails, how brothers and sisters interact."

And she challenges the idea that the books have simply taken the themes of school and fantasy from other classic children's books.

"It might have all these elements and have themes in it that really feel familiar because they're repeated in a lot of literature. But it's done in quite an original way.

"I had a grandparent in and she was saying she was so relieved the books were so well-written. She was quite happy for her grandchildren to read it."

The Harry Potter phenomenon would not have happened without the unusually high adult interest. It was something that publishers Bloomsbury picked up on.

"They brought out adult covers for some of them. They did that because a lot of people on the London Tube were wanting to read them but felt embarrassed to get them out in public on the train."

How times have changed. Those who initially dismissed the whole thing as a fad are now buying the books to see what the fuss is about. And, says Philippa, grown-ups are proud to be seen with Potter in public.

"You can get interaction because strangers will come up and say 'it's really good - have you got to that bit yet?'"