This is caused by optimizations of the WebView (which we use for rendering) on Android 5 and above.
To resolve the issue please update the Android OS on your device (firmware update).
Once this is complete please check Play Store for "Android System WebView" and update it if there is an update available.
Finally please then update the Ebook Reader app. This should then resolve the white space issue.
Kindle Fire uses a version of Android as it's operating system (OS), but Amazon updates the WebView and bundles it in to it's OS updates. If you have a Kindle Fire please try updating the Firmware (OS) using the steps below:
1. Make sure your Kindle Fire is connected to the internet, then open the Settings app
2. Scroll down and select the "Device Options" tab
3. Select "System Update"
4. Press the "CHECK NOW" button and, if a new version is available, select it.
If there is an update then after it has finished installing please try the ebook again.
Whichever device you have, if you are still experiencing the same issue please contact our support team. Please state what version of Android you have installed on your device, and what version of the Ebook Reader app you have installed, and please state if it is a Kindle Fire device.