Writing took about 2 months IIRC. But the learning took >1 year :p

I would be really interested to hear about the learning process. Was there something in particular that you read that was especially helpful? Did you buy other e-books to learn how to write and market e-books?

It started as an experiment to apply what is described in the 4 Hour Work Week book, Muse Project chapter. I've learned about marketing and ebook publishing mostly by looking at how others did it. http://javascriptrocks.com/performance/ came out a little bit before mine so I was inspired by it a little.

2 months of work for $6000? While making money probably wasn't the only reason for doing it, isn't that a pretty bad payoff? I know you will keep making sales, but (especially for technical writing) it will have a short shelf life...

The kind of technical books that have short lives are ones about specific products/versions. This is a book about creating programming languages by the sounds of it.

Other books in this field are still available at my local mass market bookstore after 15-20, even 30 years in print.

Look at TAOCP how old is that now? Like 40 years?

It took him 2 months but we don't know how many hours per day. Also this was the first book he wrote, maybe with the next one he'll make 6000 in one week. You can't expect to win big the first time.

If it's a good book, maybe he can revise and update it, add more chapters, and make a 2nd edition (with a new marketing campaign behind it).

Of course I was not working full time on this. Most publishers give an advance of $6K when writing a full book, which can take a year or so. Nice article about this: http://beginningruby.org/what-ive-earned-and-learned/

No. That's a pretty good payoff.