Calibre
Manages, converts and reads your ebook library on your own computer.
Instead of Kindle's walled library, Apple Books
S · ToolOpen sourceFreeNo accountWorks offline
Kovid Goyal started Calibre in 2006 so his e-reader would work on Linux, and it has grown into the standard way to keep your own books in order. It converts between formats, edits them, sends them to your reader and fetches news from the web. Your library is a folder of files you can open without it.
That makes it the opposite of an ebook store that rents you books and can take them away. The interface is dense, so beginners may feel buried, and a project this big leans heavily on one lead developer. Since 2025 it can also connect to AI models, including ones you run yourself, so check its settings before you use that.