It's been mentioned in some of the glowing reviews for RPG Disco Elysium (our reviewer gave it 92%) that its unique setting was created for a tabletop RPG Estonian designers, ZA/UM, have been playing together for 10 years. According to an interview lead designer and writer Robert Kurvitz had with Escapist Magazine, he's also written a novel in the same setting. It's called Sacred and Terrible Air, and it's going to be translated into English next year.
Kurvitz has other plans for Disco Elysium in the future, and is apparently planning both an expansion of some kind as well as a sequel. "We have an insanely ambitious list of projects we want to make in the Elysium setting," Kurvitz said. "The last one I want to make, when I'm 50 or 60, that I want to absolutely go crazy on and throw out all commercial considerations and get this as conceptual as possible, is the tabletop setting. The working title for the tabletop setting is You Are Vapor. It will be a really, really, crazy pen-and-paper game."
ZA/UM also plan to release a manifesto next year. I can't think of many studios who could get away with a manifesto, but ZA/UM are definitely one.