What the adaptation-extension distinction was intended to address was additive comprehension, a term borrowed from game designer Neil Young, to refer to the degree that each new text adds to our understanding of the story as a whole. So, the Falling Skies graphic novel is a prequel which tells us about the disappearance of the middle brother and thus helps to provide insights into the motives of the characters on the Turner television series. In this case, additive comprehension takes the form of back story, but the same graphic novel also helps us to better understand the organization of the resistance movement, which we can see as part of a world-building process. Most transmedia content serves one or more of the following functions:
Offers backstory
Maps the World
Offers us other character’s perspectives on the action
Deepens audience engagement.