To give you the quick and dirty, Avatar surrounds a boy named Aang who lives in a world filled with martial arts and magic that is primarily comprised of four tribes of people, each who control a particular element (i.e. fire, air, water and earth). Within those tribes are folks called "Benders" that can manipulate their native element; and throughout the land, there is one person capable of bending all four elements called the Avatar, who helps to balance the world and elemental powers. Aang is the latest in the long line of Avatars and shortly after his birth goes missing. Seeing an opportunity, the Fire Nation destroys the Air Nomads in hopes of killing Aang and therefore reigning supreme, since the Avatar won't be around to restore balance. Aang reappears after the world has gone to shit and is confronted with the responsibility of restoring order. The story goes on from there, but you get the idea
If you happen to catch the show on DVD, you'll get a better feel for the storyline and some of the Hindu and Buddhist philosophical undercurrents that Shyamalan is drawn to. Despite being a cartoon, Avatar has some surprisingly approachable depth.
One wonders, though, why Shyamalan might latch onto a project like this given his past work; all of the auteur's previous films have been written and director by him. To now adapt someone else's material - Shyamalan, however, did write the script - is an interesting move on his part, but to do so with a project so focused on visual spectacles is even more interesting. To his credit, Shyamalan states that, "It can't be special effects for the sake of special effects." However, Avatar doesn't really have the 'prize in the cereal box' like his other projects.
Is this a new direction for Shyamalan - work that is less flirting and discovery and more conspicuous and stunning? I really enjoy the guy and the storyline seems pretty intriguing, so I'm all for it. If you're curious to learn more, be sure to read the entire interview with Shyamalan over at Empire.