I’m going to be doing a series on SF novels, of which this is the first. A lot of it will be taken from Gollancz’s SF Masterworks series.
The Forever War is about a war between Earth and the Taurians, after both races discover wormholes in space which allow them to travel vast distances. In reality, though, it’s about the Vietnam War, in which Joe Haldeman took part.
The SF conceit of this novel is that the relativity involved in travelling vast distances means that time passes differently for some combatants than others, meaning that when a spaceship turns up for a battle, it has no idea whether its opponents might have developed its weapons technology beyond anything it might be able to cope with. Also, the soldiers have their lives essentially ruined by orders from above which might mean everyone they knew will have died by the time they return from a mission.
I say all this, but actually the novel doesn’t explore these ideas too much. It probably in fact has more to say about how humans can cope with the g-force involved in sudden evasive manoevres in space. But mostly it’s just a story of one man living through this experience, at the whim of his duplicitous superiors. The introduction by Adam Roberts claims it’s not the SF elements as much as the human character of the narrator which makes the novel; I remain uncertain, though I did find it enjoyable.
One SF trait I find generally annoying which this book shares is that certain humans are shown as having undeveloped psychic powers. Philip K Dick is another one who likes this trope (prior to the series I read Martian Time-Slip, where again such characters appear). I find this all to go against a fundamental grain I expect in SF, which is that it should have nothing whatsoever to do with religion and superstitious nonsense (I fear I’ll be coming back to this idea again and again). We don’t have latent psychic powers; people who claim they do are charlatans. (Technology to give us psychic powers, on the other hand, is perfectly allowable).