Open Source Android eBook Readers

CoolReader is fast and small cross-platform XML/CSS based eBook reader for desktops and handheld devices. Supported formats: FB2, TXT, RTF, DOC, TCR, HTML, EPUB, CHM, PDB, MOBI. Platforms: Win32, Linux, Android. Ported on some eInk based devices.

KOReader is a document viewer for E Ink devices. Supported fileformats include EPUB, PDF, DjVu, XPS, CBT, CBZ, FB2, PDB, TXT, HTML, RTF, CHM, DOC, MOBI and ZIP files. It’s available for Kindle, Kobo, PocketBook, Android and desktop Linux. Runs on embedded devices (Cervantes, Kindle, Kobo, PocketBook, reMarkable), Android and Linux computers. Developers can run a KOReader emulator in Linux and MacOS. Multi-lingual user interface with a highly customizable reader view and many typesetting options. You can set arbitrary page margins, override line spacing and choose external fonts and styles. It has multi-lingual hyphenation dictionaries bundled into the application. Custom UI without animation, with paginated menus, adjustable text contrast, and easy zoom to fit content or page in paged media. Look up words with StarDict dictionaries / Wikipedia, add your own online OPDS catalogs and RSS feeds, share ebooks with other KOReader devices wirelessly.

Myne is a FOSS Android application to download ebooks from Project Gutenberg, it uses GutenDex API to fetch metadata of ebooks in the backend.

TachiyomiJ2K is a free and open source manga reader for Android 6.0 and above. Based on the original Tachiyomi.

Librum is an application designed to make reading enjoyable and straightforward for everyone. It's not just an e-book reader. With Librum, you can manage your own online library and access it from any device anytime, anywhere. It has features like note-taking, bookmarking, and highlighting, while offering customization to make it as personal as you want! Librum also provides free access to over 70,000 books and personal reading statistics while being free and completely open source.