One of the great things about Kindle readers is that you can read old books for free. You can grab an epub from places like Monergism, Gutenberg, Standard Ebooks, or Planet Ebook, and side-load them into your device. The problem is that Kindles don’t support epub files, and so you have to convert them to something it can read. Historically, the advice has been to convert your epubs to mobi files. However, in 2022, the mobi file format is outdated, and instead we should be using KFX. Unfortunately, though, the KFX file format requires a bit more work to convert than mobi. It’s definitely worth the effort though because the resulting files look much better on your device. It’s worth doing for the improved typography alone. Once you set up all the pieces, converting additional books is easy.

What you will need:

• Calibre
• Calibre KFX output plugin
• Kindle Previewer 3

Once you install these three pieces, here are the steps to convert your file:

• Import your epub to Calibre
• Use the “Convert books” button
• Select KFX as the output
• When finished, use the “Send to device” menu to send the KFX file to your Kindle

You will notice that Kindle Previwer is never actually used directly. You don’t have to worry about how to use it: the KFX output plugin uses it to create the new KFX file for you automatically.

I have been using this system for years, and it has dramatically improved my Kindle reading experience.