For the Nook HD and above...
Occasionally, we enter our books in the Amazon Select Program. During this period, sales of the eVersions of the books are limited to Amazon devices and apps for the Kindle.
To read titles entered in this program, you can download the Amazon Kindle app for your PC, Android Device, etc.
Here are the links to obtain these apps:
(For the Nook HD and above.)
Kindle for PC - Read Amazon Kindle titles on your PC
Kindle for Android - Read Amazon Kindle titles on your Android device, Phones, Tables, etc.
Kindle for iPad / iPhone - Read Amazon Kindle titles on your iPad or iPhone.
Kindle for Nook HD and above.
For Older Nooks...
If you have an older color Nook or Nook Tablet, you can upgrade your operating system so you can run the Kindle app for Nook on it.
The upgrade costs $19.95 for instant download, or $29.95 to receive it by mail. Getting this upgrade is recommended as it will also allow you to download Google Play apps for your older Nook.
Click the N2A cards link on this site: