If you received a “Not enough memory” error when downloading a title or app on your NOOK, there may not be enough storage space on your NOOK’s internal memory to download the title you are attempting to download.
Archive Unused Content
To remedy this error, we suggest that you simply archive titles or apps in your Library that you are currently not using to increase the available storage space on your NOOK.
Archiving a title will move the title to from the Library on your device to the NOOK Cloud. This means it is still in your account, and you can download it when you want to access it again in the future by unarchiving it.
After you have archived a list of titles, increasing the available storage on your device, try downloading the new title again.
Alternatives to Archiving
If your NOOK has a MicroSD card slot, you can use a MicroSD Card to transfer and save books and apps to the card as opposed to your NOOK’s internal memory.
Remember to verify that you are running the latest software on your device, which also might help increase available space.