Although this video does a great job describing/demonstrating/promoting the transmedia campaign. I found the following excerpt to be the most enlightening on HOW this was done:
“The first task was to try to reduce the story to its essence—no small task for a series with 19 main characters and dozens of supporting characters from seven royal and noble families and a half-dozen other groups. He managed to get it down to “the power struggles and secret liaisons of dynastic families vying for control of a mythical kingdom”—not quite as pithy as “The Sopranos in Middle Earth,” which is how one of the screenwriters described it, but still not bad.” http://www.deepmediaonline.com/deepmedia/2012/01/and-the-final-lesson-from-game-of-thrones-is-always-support-the-bottom.html
Reducing the story to it’s essence …
This holds true in all transmedia marketing exercises – reduce the story, the value proposition, the brand promise the … whatever … to it’s essence.