It's really about two brother princes who each want control of their family's oil-rich kingdom, and their various 'backers.' The elder prince is more progressive and Westernized (and has a more humane big picture of the world), but the younger, a silly, playboy traditionalist, is favored.
Also involved are a ****-up CIA man who's grown a conscience, a business analyst who specilizes in the oil industry, and the US government. There's another substory involving some poor Pakistanis who are brought in to work the oil fields and then left hanging when a corporate merger happens. There's some arms trading on the side that goes wrong.
I saw it about three nights ago. It's a really interesting movie in a lot of ways. I liked it very much. It's structured like many novels, with every 'chapter' or scene going to a different character and part of the world. There are about 5 places of action, then, and they eventually start to come together. I love the structure and the way the story is unfolded.
I also like the moral ambiguity, although, of course, American ignorance and greed are (as usual) the evil that drives men to pointless action. But, overall, I think it does a good job of working through the complexities of the ramifications of 'easy' no-brainer money decisions made by corporate CEOs in the US. No one in the movie is unscathed, and people are only jostled into sympathetic, humane actions by personal tragedy. In that sense, it has a very John LeCarre feel to me, particularly his later work.