One of the biggest future shocks he receives is to return from a mission and discover that the entire planet has gone gay thanks to selective breeding and eugenics. The homophobic Mandalla doesn't just have to cope with his mother becoming a lesbian. Indeed, Haldeman also shares Heinlein's enthusiasm for investigating alternative sexual mores.

They didn't agree on politics – but they did have a lot in common. Small surprise then that far from disparaging Heinlein, Haldeman actually said he treasured a letter Heinlein sent him complimenting The Forever War more than the awards the book won.

Both writers also share an ability to invoke the thrill and fear of blowing shit up. Just as in the earlier novel, some of the best sequences in The Forever War centre around brutal boot camps and futuristic military equipment. Much of the book seems to have been positively inspired by Heinlein's bug-blasting epic – and the two share many virtues. It's not surprising, therefore, that the book is often described as the anti-war answer to Starship Troopers – but that's an oversimplification. Mandella, it's safe to say, does not enjoy being a soldier. The writing is admirably matter-of-fact and concentrates more on vivid description than overt emotion, but that just makes the controlled fury of the narrator's voice all the more stark. So he re-enlists and spends several more years of his life, and several hundred years on earth, fighting in a war he doesn't understand, against an enemy he doesn't dislike, watching almost everyone he knows get blown to pieces. It's too violent, too many customs have changed (even his own mother has adopted the kind of homosexual relationship encouraged by authorities eager to control the population) and too few people understand what he has gone through. Only two years have passed for him, but thanks to a quirk of relativity and the fact that he's been travelling near the speed of light, a full decade has passed on earth. He hates fighting – but finds the return to earth even more upsetting. In 1997, the novel's hero William Mandella ( a near anagram of the author's full name Joe William Haldeman) becomes one of the first batch of recruits sent into the far reaches of space to do battle with a clone-based species called The Taurans. The Forever War is a clear attempt to come to terms with that experience – even if it's set light years away. Like so many others, Haldeman was conscripted against his will, plunged into horror, wounded and dropped back into a society that now felt alien to him.

The forever war 1974