Most authors find it difficult enough to imagine just one future.
Haldeman though seems to have no difficulty conjuring up many believable variations. As future population density increases, homosexuality becomes more and more acceptable until at one point people consider heterosexuality antisocial, an emotional dysfunction and almost completely wipe it out. The super space suited humans fighting aliens theme closely resembles Starship Troopers but the attitude toward war comes from the opposite point of view. And like a good neighbor, these characters and this book quickly become good friends.