I am interested in knowing if a particular type of product exists, that is a campaign setting entirely divorced from a game system.
I am not looking for a list of products (though a single example would be nice). I might be interested in financial/sales information, but I know that's a stretch for the industry.
I am working on designing the setting for our next campaign. My goal is to have a setting that I know well enough that I can can run a successful sandbox game ( I am sometimes poor with improv, so having some points to extrapolate from is helpful ). After outlining the content I want to create before we begin play, I realized that I am essentially writing a sourcebook for a campaign setting. As I'm not sure of the game we're going to play, it is currently system free.
This made me curious if products like this exist, and if they do if there have been any financially successful ones.
With the changes and extra information, would this be an acceptable type of question?