So I'm working on Fractured Realms, that "coming soon" thumbnail to your right that's been there for about a year.
Believe it or not this book really exists and indeed is almost done! It's not actually vaporware.
Anyway, in writing the book, I realized one of my favorite things about writing- no matter how many books you write, and I've written over a hundred if we count my short PDFs- you're still exploring the unknown.
For example, in the Fractured Realms there's a group called the Aerie. They're a thieves guild but a huge one. Really more like the Five Families of the Mafia.
I had an org chart for them that dates back to my homebrew campaigns of the 80's and that's it. A handwritten org chart on a sheet of paper.
As I was working on the book though, I realized that would be insufficient and so I've spent the better part of two days nailing down what the responsibilities of each position in the Aerie has and what benefits are granted by membership.
In short, something I made do with 1 sheet of paper written by hand has become much more once I started to think about what someone else would do with that sheet and what my responsibilities were to represent the largest criminal organization in my world to a paying customer.