Amazon.com has unveiled its new slimmer Kindle digital book reader, with more storage and faster page turns, but the price tag remains the same at $359.

Amazon has improved the design of the previous model, which many had criticised for being clunky and unattractive. Kindle 2 has a longer battery life and a bigger memory, making it capable of holding many more books.

The Kindle, although a small slice of Amazon's business, has attracted a huge interest from investors and consumers as it has helped the long-predicted move to digital reading to become a reality. Analysts have estimated that Amazon sold half a million Kindles in 2008 and the product was sold out over Christmas.

The new Kindle is available for preorder and will ship from February 24, the company said. The device is still only available in the US. An Amazon spokesman in London said: "We are looking internationally and we know that customers are looking forward to getting their hands on a Kindle but we have no announcement to make at this time."

BACKGROUND

• The Kindle reviewed

Review - Amazon's Kindle e-book

My overwhelming sense after playing with the Kindle is that it is too little, too late to keep up with other technology

• The digital reader that will provide 200 books at the touch of a button

Multimedia

• BLOG: what is Amazon waiting for?

• BLOG: my love for the Kindle

Amazon shares fell nearly 1 per cent to $66 after the launch of the product at New York's Morgan Library by Amazon CEO Jeff Bezos.

Bernstein Research analyst Jeffrey Lindsay said the new Kindle was an improvement, but its price showed Amazon was not moving aggressively to make the device mainstream. "Really we don't see them as having taken the device to the next level," he said. "We think it's an incremental step of improvements. They're advancing very conservatively."

While the previous Kindle could store more than 200 titles, Kindle2 has two gigabytes of memory allowing it to hold more than 1,500 books.

It has 25 per cent longer battery life, Amazon said, and can go four to five days on one charge with wireless on and for over two weeks with wireless turned off. Amazon said a new "Read-To-Me" feature "converts words on a page to the spoken word so customers have the option to read or listen.

"Customers can switch back and forth between reading and listening and their spot is automatically saved," Amazon said. "Pages turn automatically while the content is being read so customers can listen hands-free. Users can choose a male or female voice to read to them and choose a speed."

The new version sports a new five-way controller that allows users to jump between articles and sections of newspapers. The power charger is more portable and a cover that comes with the device is more secure, the company said.

Amazon launched the first Kindle in November 2007. It allows users to read books and newspapers wirelessly on a device weighing less than a typical paperback. Users can also wirelessly download newspapers, magazines, blogs, and personal documents. Amazon's Kindle Store offers more than 230,000 books including most of the New York Times bestsellers.

The Kindle's main rival is the Sony Reader which retails for about $400 in the US. It can hold about 350 digital books and it can also play MP3 and AAC digital music with headphones. With the Sony Reader, books have to be downloaded via a PC.

Google has just launched its rival into the digital book reading market. Consumers can download books onto their mobile phones using Google's Book Search featuring 1.5 million public domain books, which have all been optimized to fit a mobile screen. The feature is only available for the iPhone and the Google's Android platform G1 phone so far.