Please can you ensure that you are updated to the very latest Ebook Reader app version.

Then open up the app, log out, then log back in.

Then resync your books.

This will resolve the issue.

Alternatively, you may receive this error message if you have bought an ebook package (more than one ebook in a single product).  For more information see the help article here.

If you are still having difficulty please contact our support team.

Depending on your version of Ebook Reader the steps needed to log out and log back in may be different.

Steps for the most recent version:

On your device, open the Ebook Reader app.
Press the Menu icon in the top left to open the menu
Select "Settings" at the bottom of the menu
Scroll to the bottom of the settings page and select "Logout"
Press "OK" to confirm you want to log out

Then back on the app's main screen press the Menu icon in the top left to open the menu
Press the menu item titled "Login to eBooks.com"
Enter your username and password and press "LOGIN"

Steps for older versions:

On your device, open the Ebook Reader app.
Press the Menu button in the top right and select Logout (if you do not see the option to logout, don't worry, just proceed to the next step)
Once you have logged out, press the icon in the top left that looks like a circle with an arrow
Log in again using you account details