Years ago, with the Thrawn Trilogy, Star Wars started a series of novels that came to be called The Expanded Universe and also contained the Dark Horse comics and video games. The Expanded Universe picked up where the movies left off and were all in-continuity (the EU's continuity, but they were all still connected).
G.I. Joe has had some novels in the past and recently had the Tales Of The Cobra War from IDW which didn't get that much attention.
But what about a series of novels for G.I. Joe? Trilogies, 9 part epics, single novels, etc... All in it's own continuity.