These days a lot of FPS games are caught up in flash, pointless sidequests and convoluted stories you won't pay any attention to anyway.
Duke Nukem is not one of those games.
Duke is a brainless, fun shooter with more attitude and machismo in it than a gun store filled with an army of Ted Nugents. The premise is simple; aliens are invading. That's it. You're dropped into the mighty boots of Duke Nukem and asked to slaughter your way from A to B (with the occasional stop at a stripper).
There are other games like this, of course. Painkiller, for one (here on GOG!), but before Painkiller, before Serious Sam, there was Duke. Not playing this game is like disrespecting your elders.