I guess it is probably 1000 words a day on average. I don't know whether the book have plots, graphs and other illustrations.

It is fast writing, but doable. It requires knowing the subject in advance well--that's a given--consistency (starts and stops double the time, the longer one writes, the easier it becomes), and to copy and paste here and there paragraphs and articles that one has written and saved through their career--there are many "additional_material.txt" in my folders.

Thanks. The book ended up as 61,000 words - which is not that much compared to all-text books - but lots of pages of resume examples. A "normal" 200 page book could have up to double the number of words (100-120K words). Just want to add that detail, as a "normal" 200-page book in two months would be much more impressive.

I originally aimed for a ~40 page book - a PDF initially -, assumed it will have a few chapters at most. As I started writing and pulling in more advice from recruiters and hiring managers, the chapters added up.

In what is pretty usual for projects you do the first time, I under-estimated the scope, as well as the time it will take. My original budget for time was a month. Not too different from some software projects in a completely new domain :)