I had been watching various Post Mortem talks on YouTube, which are essentially talks from the developers about games past their shelf-life. This PDF stuck out from the Diablo "Post Mortem" I watched. It's the original pitch for Diablo, and is only 8 pages long. Who knew how influential it'd end up becoming? Not that Roguelikes weren't done beforehand, but Diablo certainly left a mark on gaming culture as a whole.