"Avatar" was not originally a graphic novel, nor was it a comic book series with lore or a history. So some controversy surfaced here on CBM. Well, hold on to your hats nerds, here it is straight from the horse's mouth. James Cameron was questioned about the possibility of a possible book and comic book, and he mentioned something called a "Pandorapedia".
When questioned about comic-books, Cameron said:
(the following is from an interview from another website)
James Cameron: Yeah, we’ll do as much as possible to do. I wanted to get the bible worked out so that these things didn’t generate conflicting ideas or conflicting plotlines with things I would want to do in the sequels, or with each other. That was the purpose of generating Pandorapedia, working out the backstory and the future history.
JH: And you don’t have any of those deals worked out with comic creators or…
JC: Not right now, that’s really going to be a second wave, including a novel which I hope to have time to write myself.
So there you have it. Apparently, a version of Pandorapedia is available online at www.pandorapedia.com. Seems a little weak though; perhaps a big book is or will be available.

Will we see a graphic novel? It is yet to be seen.