Ryan Reynolds is generally not in anyone's top ten of actors, at least for acting. His reputation is more of smart ass pretty boy. Nothing wrong with that, but it's obvious that Ryan wanted more which explains Buried.
In this film he plays Paul, Paul in a box. Seems that Paul got ambushed in Iraq and has woke up in a coffin like box with only a lighter and a cell phone. Desperately, he starts making calls to try to get out. It's almost a black comedy as he's put on hold or told that he's being rude. Meanwhile, his kidnappers call him and make demands. They want him to make a ransome video using his phones. The folks Paul is trying to call caution that doing so would be bad for PR.
This is definitely a one man show and Ryan rises to it. His fear and frustration is perfectly done. It gives me a lot more faith that he can carry off a major film like Green Lantern. Certainly worth a watch if you aren't claustrophobic.