ePUB Reader is a robust add-on designed for Firefox, enabling users to easily open and view .epub files. This add-on supports both online and offline documents, allowing users to interact with eBooks in a seamless manner. Users can right-click on any ePub link to access the 'View ePub' option or manually input links in the popup interface. For offline usage, simply drag and drop the file into the designated area for immediate access.

The user interface provides multiple viewing options accessible from the top toolbar, ensuring a customizable reading experience. Additionally, the window can be resized according to user preference, with the content dynamically adjusting to fit. Built on the open-source epub.js library, ePUB Reader offers a straightforward and efficient solution for managing ePub files within the Firefox browser.