Novelist John Updike and rock singer James Dean Bradfield are among the big names bringing in the crowds at this year's Hay festival.
The festival runs until the end of next week
Around 80,000 people from all around the world are expected to attend the 10-day event.
It is the 17th annual festival to be held at the small market town, which is world-famous for its 40 bookshops.
Clive James, explorer Ranulph Fiennes and comedian Jo Brand will also be giving talks during the week.
The festival - described by former US president Bill Clinton described as the "Woodstock of the mind" when he visited two years ago - will see a range of events geared around entertaining children, alongside the discussions and book signings.
Politicians such as Robin Cook and sport stars like Colin Jackson and Tony Lewis are also on the list of speakers.
James Dean Bradfield will be discussing music he has written for a new play by Blackwood dramatist Patrick Jones, while former Monty Python Terry Jones will talk about Chaucer.
Festival director Peter Florence said the "glorious" thing about the event was "the mixture of musicians and writers".
"The festival's big thing is if you write in any medium, it's worth talking about," he said.
"The idea that the way Dylan Moran structures a gag and Bob Geldof structures a lyric is all basically the same thing.
"I think people can get terribly hung up on what literature might be. It's the mix," he added.
Last year Hay heard from such literary giants as Canadian Booker-prize winning author Margaret Atwood, American writer Don Delillo and Britain's Hanif Kureishi.
First-time writer Charlotte Williams won the Welsh Book of the Year for her story of her trans-continental search for her roots.
But Mr Florence said that one of the "great delights" of the festival was children's interest in it.
"They (children) have an incredible hunger for writing.
"For the first time ever kids are deciding what they want to read instead of their parents deciding for them."
The festival runs until 6 June.