A decade or so ago, I wrote one esoteric technical digital book about Unix troubleshooting. I sold it on my website at $29.95, and made enough money to justify my time. I then put it on Amazon at $2.99 and made a few hundred more.

On a dollars per hour basis, I made about $60 an hour, which was okay for the time, but I wouldn’t do it again because it was VERY HARD WORK. No, thanks, never again.