Enormous spaceships arrive at Earth and hover over Earth's major cities. Contained in these ships are an advanced race of star travellers known as the Overlords. Their task is to prevent mankind from destroying themselves and to see them into their next phase. Initially (for the first fifty years of their Overlordship of Earth) they hide themselves away from a human race not ready to see them, communicating through the Secretary General of the Unied Nations.

This is one of Clarke's highest reagrded works, and certainly it does not struggle to meet its hype. There are many influences this book has had in sf, both written and visual - most obviously being the similarities between the books opening sequence with the great ships arriving and the start of the 1980's TV Series 'V'.

But that is the only similarity between the two. The aliens here not intent on robbing the Earth for all they can get, but are benign and indeed work to see the improvement of conditions for all members of the human race and to guide the race towards it's future.

For a short novel this book certainly has a grand scale. The story plays over many years and over vast distances of space, but does so in an seeming effortless and easy to read manner. There are many little 'visits' to areas and peoples and times. These individual passages allowing the reader to feel the scope of this work. If it is possible to write on an epic scale in under 200 words then Mr. Clarke has done so here.