Furthermore, Amazon's strategy isn't limited to sales of e-reader hardware. Rather, Kindle software is available on a variety of digital devices, including the iPad, iPhone, and iPod touch, numerous Android smartphones and tablets, and Mac and Windows PCs. In other words, Kindle users can read e-books on dozens of devices, even if they never own an Amazon e-reader.

As a result, it's unlikely that Amazon will release Kindle sales figures anytime soon.

Contact Jeff Bertolucci via Twitter ) or at .