ONCE the preserve of those seeking literary diversion on long car journeys, audiobooks are now in demand from the iPod generation.

There are 7.3 million MP3 players in Britain, and the under-40s now account for most sales of audiobooks. Book downloading websites are being created to meet the growing appetite for digital audiobooks; the latest, Spoken Network, a British company, begins its two services later this month. The sites already offer more than 5,000 downloadable titles.

Paul Smithson, the founder of Spoken Network, said: “For many years, audiobooks were stored away at the back of stores like Waterstone’s and Borders, and unless you were looking for one you wouldn’t stumble across them. It wasn’t the sort of thing you would purchase on impulse.

“Now it is much easier for people to come across these audiobooks. One thing we were constantly surprised by in the research we’ve done was how many people who wouldn’t have previously considered buying an audiobook as a CD or tape said they would be interested in downloading one.”

Spoken Network, whose services begin on May 19, has the backing of nearly 50 international publishers, including BBC Audiobooks, HarperCollins, Time Warner, Hodder Headline and Simon & Schuster. It hopes to compete with the more established American companies that dominate the market.

Audible, an American company that set up a British website last June, watched its sales grow fourteenfold over five years to top $63 million (£34 million) in 2005. According to the Audio Publishers Association of America, the US audiobooks market is worth $832 million. The British market is estimated at $70 million. Eileen Hutton, associate publisher at Brilliance Audio, the largest independent publisher of audiobooks in the US, and which has signed a deal with Spoken Network, said: “We think the future of the industry is in downloads to MP3 players, iPods, etc. A recent survey of young people in America found that many people were dispensing with traditional media altogether in favour of downloadable audiobooks and music.”

BBC Audiobooks has 1,000 titles available to download and believes that its digital book business will double every 12 months for the next few years. The BBC said: “The market for audiobooks on CD is not necessarily a growing market. But downloads are growing massively. We have found new audiences for our titles through the downloadable audience.”

The most popular narrators include Stephen Fry, Alan Bennett, Martin Jarvis and Anthony Head. Although the audiobook charts are dominated by well-known voices reading bestsellers, the relatively small cost of turning a book into a digital audio file could encourage publishers to showcase their smaller titles.

Downloading sites say that digital titles are cheaper than CD versions of fiction and non-fiction. Mr Smithson said: “Prices on our site vary a lot. Some are free and others range from £1 to up to £60 for something expensive like the Bible. We compare our prices to the normal recommended retail price and we think our downloads are about 35 per cent cheaper.”

The Times compared prices of Audible’s downloadable audiobooks to CD audiobooks sold on Amazon. Sheila Hancock’s biography of her late husband John Thaw, The Two of Us, cost £3.74 less on Audible, allowing for Amazon’s postage and packaging costs. But Audrey Niffenegger’s The Time Traveller’s Wife, which is an audiobook bestseller both on and offline, was £3.98 more on Audible than Amazon.

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