This film is an excellent all-around package, as long as you're not overly addicted to slambang mindless Hollywood productions. The actors were every bit the characters they played, and the story makes you think about the issues of brotherhood, taking sides, growing up, the impact of colonialization on far-off lands.
The cinematography is gorgeous, spanning the North African landscapes in all their vastness, adding to the viewer's understanding of the isolation the tribal people lived with. (It also made me want to ride camels...) While this movie takes place in WWI, it is not a "war movie." Yes, there is a British soldier and an element of culture clash when he seeks help from young Theeb's brothers. But the story has much more to do with the character of the boy Theeb, the dilemma he finds himself in when trying to balance survival and loyalty, and the reminder that while empires fight their wars, local populations are far more concerned with going on with their lives.
While the movie is serious, I didn't it find it at all depressing. Thoughtful treatment, and pitch-perfect acting and direction.