The document touches a number of very important topics. It teaches you how to prepare promotional materials, how to make nice screenshots and get hold of journalists. It’s a great set of advice for developers, who do not yet understand how to sell their game to the press.
It also shows how to work with social channels, how to conquer Reddit and how to respond to feedback. Maybe this is not the biggest encyclopedia, but it’s a nice thing to try for a start.
You can find the full PDF here.