If you're thinking about seeing Donnie Darko, rent it and watch it (with the lights on). You will be very confused. Then read its Wikipedia article and marvel at the sophistication of the concept and plot. And how the director doesn't seem to understand that things like, say, the whole frickin' idea of the movie should probably be in the film itself.

Seriously, it's very confusing, but once the plot is explained it makes a great deal of sense—and like opening a box and looking at an entangled particle, the confusion of the last two hours suddenly turns into entertainment. The movie itself is proof of time travel.

Unfortunately, I can see why the Goth kiddies love it. A shallow interpretation would be incredibly appealing, and even a proper one leaves a lot for them to enjoy.