Ok - I confess I am a huge fan of Joe Haldeman so this might be somewhat biased.
This is not the hard Sci-Fi of "The Forever War", "Mindbridge" or "All My Sins Remembered" but is closer to "Tool of the Trade".
Anyway, the basic story is that, in the not too distant future, the people of Earth are once again walking down the path to a World War. A message is received on earth from a ship that is one tenth of a light-year away, travelling at just under light speed -both of which are well beyond Earths technology. The message is "WE'RE COMING". The story relates the events leading up to "The Coming" and how it affects the discoverer of the craft and the people who live and work around her.
As ever Joe Haldeman creates the structure of a believable society with heros, villains, the normal and the strange. Again he uses the multi-viewpoint method of telling the story (is there a name for this?) which works well and keeps the story moving along at a brisk pace. I found it compelling reading and although the ending was somewhat predictable it didn't disappoint me.