In 2020 I wrote a book on FFmpeg after going through the entire FFmpeg documentation. I wanted to learn FFmpeg inside and out by actually using it to convert audio/video based on what the documentation offered. In the end I open sourced the results as an extension to the official docs[0] and then released in on Kindle as well[1].

In the last 4 years I've sold 743 books which is just shy of $2000. Still I love the fact that every month I'll get a KDP payout email and it feels more gratifying than my own FAANG+ paycheck for some reason.

[0] https://github.com/jdriselvato/FFmpeg-For-Beginners-Ebook [1] https://www.amazon.com/dp/B087GYV15Y/