After years of lurking in the literary wilderness, the e-book market has exploded with online retailer Amazon.com's digital volumes recently overtaking sales of their hardcover counterparts.

The increase in sales has come as Amazon slashes the price on its Kindle device amid heavy competition from Apple's multi-purpose iPad and e-readers from Sony and bookstore giant Barnes & Noble.

Underscoring the growth, Hong Kong's massive book fair, an annual event attended by almost one million people, wrapped up last week with visitors exposed to a brand-new section: digital reading.

Beijing-based Hanvon Technology unveiled a black-and-white tablet reader that comes with 5,000 Chinese and English book titles pre-installed for about 3,400 Hong Kong dollars (440 US).

Readers can download thousands more titles for as little as 20 Hong Kong dollars each on the device, which also lets users enlarge the typeface, take notes and look up words in the dictionary.

"One (print) book might cost you 100 Hong Kong dollars or more, and then you have to find a place to store it," Hanvon employee Bo Bo Wong told AFP. "With this, you can have thousands and thousands of books in one place," she said.

Mainland companies such as Hanvon, Acuce and Tianjin are taking on the likes of Apple and Amazon by pushing content tailor-made for the vast and rapidly growing Chinese digital market.

The total value of digital publications across all platforms overtook that of traditional print publications in mainland China for the first time last year, the General Administration of Press and Publication said last week.

According to the South China Morning Post, a recent survey by the Chinese Institute of Publishing Science found that nearly a quarter of the 20,000-plus people it surveyed now do most of their reading digitally.

The newspaper quoted Chen Fuming, a manager of a major bookstore chain in Guangzhou across the border from Hong Kong, as saying Chinese book shops were in crisis.

"Even I myself now prefer to read fiction with my mobile phone," Chen said. "It's cheap and convenient."

New Zealand's Kiwa International, another company showing off its wares at the Hong Kong book fair, is using Apple's iPad as a platform for its child-targeted software.

The Auckland firm's technology lets children interact with books downloaded onto the iPad by colouring in story characters and swiping words that are then repeated aloud -- in nine languages.

"They can totally personalise the book," Kiwa's creative director Derek Judge told AFP. "And we provide a service to (traditional) publishers who want to enter into the digital arena."

Amazon temporarily sold out of its 189-dollar Kindle e-reader last week and on Thursday unveiled a new 139-dollar model that connects online by WiFi instead of via 3G networks.

"Amazon.com customers now purchase more Kindle books than hardcover books -- astonishing when you consider that we've been selling hardcover books for 15 years, and Kindle books for 33 months," Amazon boss Jeff Bezos said last month.

US bookstore chain Borders has also launched an electronic book store to tap into the market, which has seen late Swedish crime writer Stieg Larsson become the first novelist to sell more than one million e-books on Amazon.com.

But while British author and actor Stephen Fry is an avowed technophile, he doesn't think printed books should be written off quite yet.

"Printed books certainly will continue to exist," he said at the Hong Kong fair.

"I love them and will continue to collect them... (with) some books I just want to turn the pages myself."