An engineer in Mumbai started building an ebook manager in 2006. Twenty years later, almost 3 million people across 236 countries open it every two months.
His name is Kovid Goyal. The software is called Calibre. He still maintains it as principal developer. The last release shipped a week ago.
It is free. It is GPL-3.0 open source. It runs on Windows, Mac, and Linux.
Here is what it does in plain words.
You drag an ebook into it. It reads almost every format on Earth. EPUB. MOBI. AZW. AZW3. KFX. PDF. Comics in CBR and CBZ. Word documents. Text files.
You can convert any of those into any other format with two clicks. So the book you bought on Kindle can be read on a Kobo. The PDF your professor sent can be read as an EPUB on your phone. The comic in CBR can be turned into an EPUB.
You can edit the metadata, fix the cover, add tags, organize a library of ten thousand books.
You can send the book to your Kindle, your Kobo, your Tolino, your phone, your tablet straight from the app.
You can run a small content server on your own laptop and read your books on any browser in your house.
24,978 stars on GitHub. 2.9 million active installs in the last 60 days. United States is the biggest user base at 14.8 percent, India is in the top 20, every country on the map has it running somewhere.
This is what your personal library was supposed to look like. A folder of files you own. Not a device that locks you in.
(Link in the comments)