Most of us who read SF have read works by Clarke or have at least heard about him. He is, after all, one of the most popular 'golden age' SF authors. So, by saying this I want it to be clear that Childhood's End is a classic. It was written in a time when SF had practically no foothold whatsoever in the mainstream market. Like Foundation by Isaac Asimov, Childhood's End was written in installments and published in magazines. I didn't know this when I first started reading it, but now that I do know this it makes some of my dislikes for the book less pronounced. I have to now take into account that rather than a full fledged novel, this book is more like a set of connected short stories all set in the same universe on the same plotline.
The synopsis is this:
Set in a not so distant future (at least when it was written) an alien race known as the Overlords comes to Earth in giant ships (think Independence Day, only not violent). They establish themselves as overseers of Mankind, ridding the world of war, famine, prejudice, racism, etc. All this is done without violence. The Overlords could easily wipe out Mankind, but that is not their goal. They are there to establish a long lasting peace, a veritable utopia where none go hungry and everyone can live a life of leisure.
But something else is going on, something that Mankind is not prepared for and could very well make them extinct...
That synopsis is somewhat vague simply because I cannot give anything at all away or it would ruin the ending of the book. I can tell you this, you will have one of two reactions to the end: you'll either feel sad and sympathetic, or you will be angry.
Now, stylistically speaking Clarke is a very good writer--one of the best really when you think about it. He is able to draw you into the characters deep enough to care about them even though you know them for such a short time (remember, written in short story installments).
The only thing I didn't like about the book was the ending. To me it seemed far too sudden and I can't imagine reacting in the way the characters did to the final twist. This isn't to say that the ending is unbelievable, although scientifically speaking from a more modern view it does seem tremendously unlikely, but it is saying that the ending seemed somewhat out of place. Many in my lit class discussed this same subject. Some liked the ending, others didn't. I personally didn't much care for the ending.
Regardless, this is a classic. A must read. If you are into the foundations of SF, as I am, then you should probably pick this one up, along with Foundation by Isaac Asimov and early works by Poul Anderson and the like. For a classic it is good; but from a modern prospective it lacks due to various circumstances. Still, I'm glad I read it.