The Best Free Apps for Reading E-Books (2026)
Calibre
Calibre is a comprehensive desktop application available under an open source license (GPL) that brings together e-book management and reading functionality under one roof. First developed in 2006, the application runs on Windows, macOS and Linux operating systems; however, there is no official mobile app. Calibre supports formats such as EPUB, PDF, MOBI, AZW, CBZ, EPUB, PDF, MOBI, AZW, CBZ and many more, and can convert between them. Users can edit the metadata of books in their libraries, update cover images and transfer books directly to connected e-reader devices. In addition, the app has the ability to automatically download content from news sources. Calibre does not require a user account and can work completely offline without an internet connection. While the built-in reading experience remains functional compared to other apps, the app is mainly positioned as a library management and format conversion tool.
FBReader
FBReader is an e-book reader developed in 2004. The application is available for Android, iOS, Windows, macOS and Linux platforms. FBReader supports common formats such as EPUB, FB2, MOBI, RTF and TXT. PDF, DjVu and comic book formats are supported by separate plugins in the free version; in the Premium version, these supports are integrated into the application. The app is distributed in two versions: free and paid (Premium). Cloud synchronization is included in the paid plan, while basic reading functions are available for free.
KOReader
KOReader is an e-book reader available under an open source license (GPL), specifically developed for devices with e-ink screens. The application works on e-ink devices such as Kindle, Kobo, PocketBook as well as Android platform. There is no official support for iOS. KOReader supports EPUB, PDF, MOBI, FB2, CBZ, DjVu and many other formats. The ability to reflow PDF documents to make them readable even on small screens makes the app stand out in this field. Available completely free of charge, KOReader does not require a user account and can work offline. Offering advanced typography settings, integration with Calibre and extensive customization options, the app has become a popular choice among technical users and e-ink device owners.
Librera
Librera is an e-book reader for the Android platform, available under an open source license (GPL). The app is available on Google Play, F-Droid and directly as an APK. A desktop version is available in beta for macOS, while iOS support is still in development. Librera supports EPUB, PDF, FB2, DjVu, CBZ, CBR and many other formats. It is available in two versions, free (Librera Reader) and ad-free paid (Librera PRO). With advanced functions such as TTS (text-to-speech), customizable reading profiles and OPDS catalog support, the application can work offline without requiring a user account.
Lithium
Lithium is an e-book reader for the Android platform that only supports the EPUB format. There is no official support for iOS and desktop operating systems. The app is available for free on Google Play, while the paid version, Lithium Pro, offers advanced features such as Google Drive synchronization, custom reading themes and additional highlight colors. With automatic book detection, highlighting, note-taking, night and sepia theme support, and the ability to switch between page and scrolling reading modes, the app stands out with its simple and user-friendly interface. Lithium does not have an official website, and developer communication is only available through in-app feedback.
Moon+ Reader
Moon+ Reader is a feature-rich e-book reader developed for the Android platform. There is no official support for iOS and desktop operating systems. The app supports a wide range of formats including EPUB, PDF, MOBI, FB2, CBR, CBZ, TXT and HTML. It is available on Google Play in two versions, free and paid (Moon+ Reader Pro). The Pro version offers additional features such as ad-free operation, cloud synchronization via Dropbox and Google Drive, advanced theme options, reading statistics and TTS (text-to-speech). With its highly customizable interface, comics support and OPDS catalog integration, Moon+ Reader is among the most comprehensive e-book readers on the Android platform.
ReadEra
ReadEra is a free and ad-free e-book reader for Android and iOS platforms. There is no official support for desktop operating systems. The app supports a wide range of formats including EPUB, PDF, MOBI, AZW3, FB2, DjVu, DOC, DOCX, RTF, ODT and TXT. It is available in two versions, free and paid (ReadEra Premium). In the Premium version, additional features such as cloud synchronization, transfer of reading progress to all devices and advanced citation management are available for a one-time payment. The app does not require a user account and can work completely offline, automatically detecting files from device storage.
Kobo
Kobo is an e-book platform from Rakuten, available in both hardware (e-ink reader devices) and software (apps). The application is available in mobile versions for Android and iOS, and desktop versions for Windows and macOS. In addition, Kobo Web Reader service is offered, which can be accessed through the browser without the need for any download. The platform supports common e-book formats, especially EPUB and PDF, and offers the opportunity to listen to audiobooks. While Kobo is free to use, a Kobo Plus subscription is required to access the extensive catalog. Reading progress, notes and highlights are automatically synchronized across all devices. It cannot be considered a fully open source solution due to its closed source nature and DRM implementation; however, the fact that it allows the installation of KOReader on e-ink devices positions it among the platforms compatible with the open source ecosystem.
Conclusion
With the diversification of digital reading habits, e-book applications continue to evolve to meet the different needs of users. The eight applications analyzed differ significantly from each other in terms of platform support, format compatibility and features offered. Calibre for those who need library management and format conversion, KOReader for e-ink device users, Librera and Moon+ Reader for mobile users looking for wide format support stand out as functional solutions. Users' ability to make an informed choice based on their needs and priorities will directly affect the quality of the digital reading experience.
Frequently Asked Questions
Are all these apps free?
The majority of the apps reviewed are available for free with basic functionality. FBReader, Librera, Moon+ Reader and ReadEra also offer paid Pro versions with additional features such as ad-free usage, cloud synchronization and advanced features. Calibre and KOReader are completely free.
Which app supports the most formats?
Calibre and ReadEra offer the widest format support among the apps reviewed. Both apps support EPUB, PDF, MOBI, FB2, DjVu, DOC and many other formats.
Can I download books from the internet with these apps?
The majority of the apps offer access to free and copyright-free book resources such as Project Gutenberg through OPDS catalog support. However, commercial book purchases can only be made through Kobo.
Which app should someone who uses both Android and iOS choose?
Kobo, ReadEra and FBReader stand out among the apps that support both platforms. These apps ensure the continuity of the reading experience between different devices.
Which app is more suitable for my e-ink device?
KOReader is the most suitable option for devices with E-ink screens. The app is compatible with popular e-ink devices such as Kindle and Kobo and offers a comfortable reading experience even on small screens thanks to its PDF reflow feature.
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