The Koala Reader is based on PageTurner.
It has two extra features.
1. A free English to English dictionary. Long press the word and it's meaning will pop up.
2. Add your Shanbay username and password in the preference. Then you'll be able to login in to Shanbay and add words to your word book.
Thanks to PageTurner and Shanbay for your excellent work.
You can find the source code here: