I'm not into the games - haven't the time or the inclination. but i love the stores and have started reading the book Van Horstmann, enjoying it and intrigued. So I've been googling Warhammer more broadly and trying to understand how the book writing works. there's so many authors on so many different aspects of Warhammer 40K, Fantasy and Heroes. I don't understand who gets to write them and who chooses the angle that gets focused on. Are they commissioned or are they more like fan fiction? anyone here can shine some light please?