I wrote in detail about the process of writing, marketing, and releasing my first book here:
https://adamwathan.me/the-book-launch-that-let-me-quit-my-jo...
And was interviewed on IndieHackers to talk about the most recent one here:
https://www.indiehackers.com/podcast/098-adam-wathan-of-refa...
If the work is a good match for your skills and personality it’s a really great way to make a fantastic living.