Man, what a great question! I've been obsessed with 'Avatar' ever since it hit theaters, and I love digging into its origins. The film was actually an original screenplay by James Cameron, who spent years developing the concept and world-building. He famously wrote a 150-page treatment back in the mid-'90s but waited over a decade for technology to catch up to his vision. The lore of Pandora, the Na'vi, and even the unobtanium mining conflict were all crafted from scratch—no pre-existing book or novel. That said, you can totally see influences from classic sci-fi like 'Dune' or even environmental themes reminiscent of 'FernGully,' but it stands on its own.
What’s wild is how much supplemental material came afterward. There are novelizations, comics, and even lore books expanding the universe, but they all followed the movie. Cameron’s world was so rich that it spawned its own extended universe, which is rare for an original screenplay. If you haven’t checked out 'The Art of Avatar' book, it’s a must—it shows how much thought went into every detail, from bioluminescence to the Na’vi language. Makes you appreciate the originality even more.