Daniel Radcliffe stars as the boy wizard
Radcliffe, 12, made his admission about Rowling's four best-selling stories about the boy wizard in an interview with next week's Radio Times, published on Tuesday
He said: "I read the first two when I was eight or nine but I found it really hard to get into them - I couldn't get into any books when I was that age."
The movie version of the first Harry Potter book will be released on 16 November and is expected to be a global blockbuster.
In the interview, its young star added that he was looking forward to huge fame.
"I have thought a lot about being recognised and I think it will be quite cool," he told the Radio Times.
"I'm just going to enjoy it - after all, I might do this film and then disappear, or something might go horribly wrong and I'll never act again.
"Or in a couple of years I might have changed so much that I look wrong for the part - even though Harry grows with the books. So I just want to enjoy it while I can."
Preview
Radcliffe said that he never imagined winning the part in Harry Potter and the Philosopher's Stone, as the film will be known in the UK.
"I thought it would be really cool just to be able to say I auditioned for the part - I never thought I would get it," he said.
The excitement over the release of the movie - which will be called Harry Potter and the Sorcerer's Stone in the US - has been steadily increasing over the past few months.
It was heightened again earlier this week with reports of cinema-goers being left "ecstatic" after a preview screening of the movie in Chicago.
But despite the fuss - and the fact that work on the second movie had already begun - Radcliffe said he was still able to live a fairly normal life.
"I go home every day when I'm filming. So I don't miss anything about the outside world, apart from my friends," he said.
"And I still see them regularly and we keep in contact by email. They've been very good about not releasing any information about me. I think they're all just happy for me."