Yes. You can use Lumina Reader on up to six devices at the same time, provided you log in with the email address used to purchase the eBook.
To manage devices, go to Account → Registered devices in the app and unlink devices you no longer use.
- Install Lumina Reader from your device’s app store.
- Log in with the same purchase email address.
- Your library should sync automatically.
If access issues continue, refresh your library or log out and back in with the correct email address.