For fans of the human race, this book may have a depressing end.
Like a lot of science fiction, the strength of Childhood's End is not in its characters but in the ideas it explores.
The more you learn about the universe the more you realise how inconsequential Life on Earth can seem. In Childhoods's End, life on Earth evolves to the point it outgrows itself and mystically leaves to become part of the greater cosmos.
Humanity dies out, with the last human issuing a running commentary as the Earth unravels into the fabric of space.
Ironically, the alien race that comes to Earth to guide humanity through this final phase has reached its evolutionary peak, and is unable to move to the higher state of being that humanity is being ushered towards. While you are left pondering the prospect of humanity being swallowed up into a "higher purpose" and losing its own place in the universe as a consequence, you begin to feel an affinity with the aliens who are left to search for their own significance in the grand scheme of things and their determination to not die out as meaningless bystanders.