Childhood's End - Arthur C. Clarke

Earth has become a Utopia, guided by a strange unseen people from outer space whose staggering powers have eradicated war, cruelty, poverty and racial inequality. When the 'Overlords' finally reveal themselves, their horrific form makes little impression. Then comes the sign that the Overlords have been waiting for. A child begins to dream strangely - and develops remarkable powers. Soon this happens to every child - and the truth of the Overlords' mission is finally revealed to the human race...