Closer is about the key wrong move you can make in an intimate relationship.
The good. Nice music and score. Beautiful photography. Solid characters with great depth. Very realistic. Excellent scenario construction which tells a long story in a very short time while making us understand what really makes or breaks a relationship. It mostly follows chronology or otherwise makes it easy to understand, but never shows any time stamp. That makes the viewer's mind work and thus plunges us into the story rather quickly, a fascinating tale of change and turnabout.
The actors. Natalie Portman gives a great performance, and shows her talent with a complex yet subtle role. Clive Owen as the clever bastard definitively gave the performance of a lifetime, it's by far his best one. Jude Law as the neurotic romantic indecisive love lorn control freak certainly gave us one of his best. Julia Roberts gave a nice performance, but it just not on par with the others.
The bad. Nothing.
The ugly. Nothing.
The result. Not for everyone, but should be watched by everyone.