Endgame is probably Beckett's second most famous play, after Waiting for Godot. It appears to have a post-apocalyptic setting, although what the apocalypse was is never defined and probably isn't the point.
(Incidentally, isn't it interesting that something that is obviously SF is allowable in academia when it's drama but not when it's a novel?)
Anyway, the two main characters, Hamm and Clov, are mutually dependent, since one is blind and one is lame. They're continually threatening to leave each other alone (and thus essentially kill each other). They ask constantly why they remain in their respective positions, and, indeed, why they do anything. They talk about nature, and culture, and meaning (lack of). Basically, the message of this play is
WHAT'S THE POINT? I MEAN, REALLY, WHAT'S THE POINT?
And no-one has any answers and, eventually, no-one cares. Happy times.