Childhood's End is a science fiction novel by Arthur C. Clarke published in 1953. A version of Childhood's End with a new introduction was released in 2001.
Warning: Wikipedia contains spoilers.
Childhood's End deals with the transformation of humanity into part of an interplanetary hive mind.
The book opens with enormous alien spaceships one day appearing over all of Earth's major cities. The aliens known as Overlords quickly make radio contact and announce their benign intentions and desire to help mankind. They also arrange person-to-person (though not face-to-face) meetings to be conducted between Secretary General of the United Nations Stormgren and the Overlord leader Karellen, although through a one-way mirror so that Stormgren cannot see Karellen. They promise to reveal themselves in fifty years, after which mankind will have become used to their presence.
True to their word, fifty years after their arrival, they appear in person. They have all the classical appearance of devils -- the red skin, leathery wings, pointed tails, etc.
The Overlords, after a hundred years on Earth, reveal their true purpose. They are in service to a being of pure energy known as the Overmind. Their purpose is to usher humanity's evolution to a higher plane of existence, high enough to merge with the Overmind. The fact that they look like devils is a reverse race memory - we knew that their coming would fortell the end of our species.
One day, humanity's children start displaying telepathic and telekinetic abilites. These children soon become distant from their parents, and the Overlords quarantine all of them to the continent of Australia. Following the quarantine, no more normal children are born. The rest of humanity ages and dies off, while the children become closer and closer to the Overmind.
Jan Rodricks, a mulatto, is the last living human being, and he will witness the final transformation. He had stowed away on an Overlord supply ship, and due to the relativistic nature of time he lived longer than any other human. By the time he returns to Earth from the Overlords' homeworld, the rest of humanity has died out. He stays behind to witness the final transformation while the Overlords depart and Earth itself dissolves away. Humanity has evolved to a higher plane of existence, and the childhood of mankind has come to an end.
