There has been some controversy and argument as to whether Harry Potter can truly be said to have transcended to be a transmedia story. As an avid fan I believe it has but what do the experts think?
Relatively little of the official Harry Potter media produced to date has been transmedia in the sense that I use the term — as an extension of the information we have available about the world rather than as a replication of the story from one medium to another. I’ve been suggesting lately that we might identify transmedia projects through the combination of two factors – radical intertextuality (that is, the complex interweaving of texts through the exchange of story-related information) and multimodality (that is, the mixing of different media and their affordances in the unfolding of the story). Pottermore works at both levels.
Pottermore brings the Harry Potter brand from its basis in being a repurposed or repeated story world, into being a true transmedia brand.
– Jeff Gomez (2011).