Do you envy your friends who are able to buy and read e-books on their Kindles, but you're unwilling to buy yet another device? Amazon may have a solution for you. Today, the online retail giant announced that Kindle apps will be made available for Android- and Windows-based devices, further growing the family of devices which users can use to read books downloaded through the Kindle app.

The new Kindle apps built for Android and Windows tablet computers will let customers engage in Amazon's “Buy Once, Read Everywhere” program. Once you purchase an e-book from Amazon, you can then read it on Kindle, Kindle 3G, Kindle DX, iPad, iPod touch, iPhone, Mac, PC, BlackBerry and Android-based devices, according to Digital Trends.

Amazon is now offering more than three quarters of a million Kindle books to Android and Windows Phone 7 users, plus Windows LCD tablet owners, with the site's free application for Android and Windows devices. If you already have a Kindle, but don't always want to tote it with you, you can take advantage of Amazon's Whispersync service, which allows you to buy and read e-books on either your phone or your Kindle.

“Many people are buying both a Kindle and an LCD tablet computer,” said Dorothy Nicholls, director of Amazon Kindle, statement. “We’re very excited to support the upcoming Android and Windows LCD tablet computers with free Kindle apps that we’ll tailor for the particular devices. Our Whispersync technology makes it simple to move back and forth between devices. Read on your Kindle, read on your tablet, read on your phone. We’ll keep track of your last page read, and make it easy.”

In an increasingly competitive market for digital readers, Amazon has been able to stay competitive by diversifying beyond the Kindle device. Other competitors include Barnes and Noble’s Nook, the Apple iPad application and the Kobo Reader.

The Kindle Store offers one of the largest selections of e-books in the marketplace. In addition to allowing users to buy a book once and read it on multiple platforms, Amazon also automatically backs up books so you can re-download them anytime.

Amazon's Kindle Store may be found at its website.