Expanding upon its "Buy Once, Read Everywhere" campaign, Amazon today announced the launch of a new cloud-based service for its popular Kindle e-reader.

The new Kindle Cloud Reader is a free application that enables users to access their digital libraries from web browsers, rather than have to download Kindle books to individual devices.

The app is based on HTML5, which allows readers to still access amounts of content even when not connected to the internet. Additionally, the reader automatically syncs with the user's personal Kindle library, meaning the user can pick up exactly from where he or she left off on a different device.

Amazon noted that its Kindle Cloud Reader is optimized for Safari on the iPad, but it also works on Safari and Chrome for Macs and PCs. Eventually, the company plans to introduce the service for Internet Explorer, Firefox and the BlackBerry PlayBook, among other mobile devices, it said.

The Kindle has become a big part of Amazon's business in recent years. According to a report from the Yankee Group, e-reader sales are expected to reach 72 million units by 2014, with the Kindle leading the way.