Lithium is an EPUB reader that offers a range of features to enhance the reading experience. The app automatically detects books and allows users to switch between pages and scrolling. It also offers night and sepia themes, as well as the ability to highlight and take notes. Lithium is built with Material Design and is 100% ad-free.

Users can upgrade to Lithium Pro to unlock additional features, including the ability to sync reading position, highlights, notes, bookmarks, and more across devices with Google Drive. Custom reading themes with custom colors and more highlight colors are also available with the Pro version. It is important to note that Lithium Pro works as a license to unlock the Pro features in the app and is not a separate standalone app.

Users are encouraged to provide feedback through the "Send feedback" button in the app's drawer or menu. The Lithium team welcomes bug reports and crash reports to improve the app's performance. While there may be occasional offers to upgrade to the premium version of the app, Lithium is 100% ad-free.

Overall, Lithium is a user-friendly EPUB reader that offers a range of features to enhance the reading experience. The Pro version offers additional customization options and the ability to sync reading progress across devices. The Lithium team values user feedback and encourages users to report any issues they encounter.