This book contains all the big ideas and plot points needed for a great story. Yet, it falls flat. The main problem I had with it is that the writer very obviously is making the plot up as he is going along. For example: the hero's relationship status is left a bit up in the air when he goes to the moon for two years. He then remains faithful to her for years and still remains faithful after he could safely presume her dead. But then he learns she got a job in a base on the bottom of the sea, so she may well be alive. But he apparently already knew that was an option. Then the nigh-omnipotent peaceful, but not friendly, aliens tell him she is dead anyway. Which makes no difference in his life, considering he never tried to find her or contact her anyway. So what was the point?
One more example: At some point it is revealed that the lunar colony had a deeper purpose, that of a place for humankind to survive the coming atomic war. That means people who had expected to return home to their families after two years are suddenly captives on the moon. But it's never made clear how the colony could hope to survive with limited food supplies.
There are also a few homicidal maniacs in the book, probably thrown in for added excitement, but since they have no sane reason for doing what they do and I know the hero is never really in danger anyway, it just annoyed me.