Arabic Reader is a free and open source eBook reader. Supports epub rtf doc (MS Word) html fb2(.zip) mobi (including non-protected kindle books) and plain text file formats. This app is customized for Arabic and Right-to-Left languages.

Arabic Reader is fast highly customizable. Can use external TrueType/OpenType fonts and custom backgrounds. Screen brightness can be changed during reading (slide finger up/down along the left screen edge). Supports different day/night color schemes.

You can download books manually and put them into /sdcard/Books catalog on your device.

This application is open source you can download the source code from:
https://github.com/boussouira/android-arabic-reader