I support everyone who writes their own textbook or programming book. It is a great use of time and I would much rather someone do this than play video games all day.

I have a few books in progress, some farther along than others, and seeing posts like this with actual numbers on revenue is extremely helpful.

After all the work he did, he made about $150k so far. Honestly that isn’t a lot of money for his expertise and the amount of time he put into it - if he moonlighted as a consultant for those hours he would have made more, with less to show for it.