turned this short story by Damon Knight
into one of the best
episodes from Serling's television series The Twilight Zone
. First aired on March 2, 1962
The alien Kanamits
arrive on Earth and start solving all the world's problems. A few warmongering generals are skeptical, but the Kanamits are here only to serve man, which they prove by giving the United Nations a copy of a book which guides them in this principle (of course it's in the Kanamits' own language).
The world disbands its armies, and the Kanamits build domes around Earth's cities. An unlimited food supply, and free energy.
They then begin offering free passage to their home world... thousands sign up, including the main character, government codebreaker Michael Chambers
Rather than spoil the rest of the story, I suggest you find a tape of the episode, or wait until it's shown on TV again.