kovidgoyal/calibre

Calibre is a free, open-source e-book manager that lets you organize, read, convert, and edit your entire digital book collection in one place. Think of it as iTunes for e-books, it keeps your library tidy, handles multiple file formats, and connects to your e-reader device to transfer books directly. The software can view and read e-books in all the major formats (like EPUB, MOBI, PDF, and more), convert books from one format to another so they work on any device, and edit the contents of e-books directly. It can also fetch metadata, things like cover art, author bios, and descriptions, automatically from the internet to fill in gaps in your library. One particularly handy feature: it can download newspapers and magazine articles from the web and package them as e-books so you can read them offline at your leisure. You would use Calibre if you have a growing collection of digital books across different formats and devices and want one tool to manage everything. It runs on Linux, Windows, and macOS. The project is built primarily in Python and is maintained as a volunteer effort with community donations.