This is the direct sequel to The Forever War. Twenty years (subjective for our heroes) have passed since the War ended. William and Marygay have settled down on the frigid planet of Middle Finger, which has the largest population of veterans that have not integrated with the “Man” group mind comprising most humans. Like most of the community of veterans, they feel alienated from the rest of humanity, which uses implants to integrate into a mind “Tree”; a group mind where individuals willingly surrender most of their individuality. The Taurans, enemies during the War, have a similar arrangement, and Man (group mind humans) have more in common with them than with the old-style humans. It is a life, but our heroes are not happy with it. They hatch a plan to take a starship forty thousand years into the future by flying a big loop at relativistic velocities. Only ten years subjective will pass on Middle Finger. However soon after departure things start going very wrong for unexplainable reasons and they must get in the lifeboats and return in suspended animation, taking decades to do so. Once back, they discover that everyone is gone, vanished simultaneously and instantaneously.
This is a very different book from the Forever War in some ways. It does not deal with war, for one thing. However the themes of alienation in one’s own society are still there. It grapples with what it means to be human, what it means to be an individual, what it means to be sentient. Without giving away too much of the ending, I will say that it also deals with God, or at least one possible interpretation of God. The ending surprised me but in a good way. It was very thought-provoking. Just as in the Forever War, the characters and plot are finely tuned, flowing nicely. Despite the heavy themes, it is not a heavy read. Recommended but read The Forever War first.