Calibre is a free and open-source e-book management software that allows users to organize, convert, and read e-books. It supports a wide range of formats, including EPUB, MOBI, and PDF, making it versatile for different devices. Users can also edit metadata, download news from the web, and sync their e-books with various e-readers. In addition to its management features, Calibre includes a built-in e-book reader and a powerful conversion tool. This enables users to easily change the format of their e-books to suit their reading preferences or device compatibility. Overall, Calibre is a comprehensive solution for e-book enthusiasts.