You don't need a Kindle device to read a Kindle ebook, provided you install one of a range of applications that can be downloaded from Amazon free of charge.
The online retailer has created a range of apps that will enable devices to read ebooks formatted for the Kindle. These include: Apple's iPhone, Windows PCs, Apple Macs, iPad, and Android OS phones. Its latest app release Kindle-enables the Windows Phone 7.
Each version of the app is available to download from AMAZON.