To the best of my recollection the 2nd Gen 8.9" Fire runs Fire OS3 which is based on Android 4.0.3
A good alternate free reading app for that might be FBReader and you can find an APK for it on the official site (look under History and current version for a download link)...
https://fbreader.org/android
To install the app on the Fire you'll need to enable apps from unknown sources (in other words not from the Amazon appstore). Settings --> Applications
Once that's enabled you can either copy the APK over via USB or use the Fire's browser to just download it directly. Tap on the APK file and it should open the installer...