That dude is a machine. He wrote 4 secret novels during the pandemic on top of several regular ones.

I'm quite intrigued by his system of writing. It's nothing magical, he works on it hard and the process is roughly connecting various ideas together. He finds interesting ideas and write them down and then when the time is to go for a book, he tries to find ideas and concepts that work together. He then writes a rough outline of a book and then goes and fills in chapters after which he gets multiple reviews/revisions before it goes out.

Sounds almost like getting a rough requirements or ideas, then writing a more detailed specification and finally fully developed software that goes through rigorous testing and refinement.

It's quite different to how I thought most writers write. My assumption it's more straightforward with little preparation.

Depends a lot on the author. The best ones have a plot line that they follow.

But many major authors produce a book every 1 to 5 to 10 years. Game of Thrones being the big example.

That's the name I think of every time someone talks about constant writing. He admits that he is emotionally very stable and doesn't suffer of ups and downs as most of the other writers.