The ending is quite trippy as it appears they have landed on a cartoon planet. In the meantime there's lots of God picking good white Christians to go to this weird world. I can't exactly figure out why God was punishing us this time. Maybe it was because of the godless Russians. He certainly wasn't picky about women who cheat on their fiancees.
A sci-fi classic, but the science is well dodgy*. The socio-political aspects are good though. Still worth a watch, even if the ending is ridiculous.
* = How can a planet (ejected from another system, having travelled through interstellar space, through our solar system, and towards Earth) be in any way habitable by the time it reaches us? Simple: you get a Hollywood script writer to make it so.