Last year, to coincide with the centenary of the Great War, a spate of books was published that covered the conflict from all angles - everything from new histories to trench-set fiction to biographies of its soldier-poets.

This year there appears to be no sign of let-up. But while scanning publishers' 2015 catalogues, it becomes quickly apparent that, even without a centenary, there is as strong a demand as ever for books on the Second World War. The titles that grab our attention are not those that retread old, churned up ground, but rather those that chart less chronicled campaigns on less documented fronts, preferably by less familiar authors. A book which meets all those criteria is a rediscovered classic and one of the most famous Finnish novels ever written.

Unknown Soldiers was first published in Finland in 1954 to mixed reviews but has since gone on to sell 700,000 copies - no small feat for a country with the same size of population as Scotland. It remains one of Finland's bestselling books of all time, one read by every Finnish child at school. Its author, Väinö Linna (1920-92), was one of Finland's most influential authors of the 20th century. For his breakthrough novel, he drew on his own experience as a machine-gunner on the eastern front from 1941-44. Unknown Soldiers previously appeared in a rickety English translation. Now, thanks to the superlative efforts of Liesl Yamaguchi, we have a version which finally does justice to the original.

The novel begins with a calm-before-the-storm mobilization of troops. On the second page one soldier-to-be learns that "Adolf was raising a ruckus". But of course when Finland enters the fray it is not to neutralise Hitler but to take up arms against the old enemy, the Soviet Union. As Linna builds up his cast, it turns out that most of his officers have just fought in the 1939-40 Winter War, at the end of which the Finns and Russians achieved only a bitter stalemate. This time around the Finnish objective is to complete the job and permanently derail the marauding Soviet juggernaut.

Once Linna's men have been set up he promptly sends them into battle - and then proceeds to pick them off, one by one. "We're headed for the cemeteries, boys!" one says grimly, not realising that the majority won't even get that privilege. Characters introduced fleetingly in the first couple of pages, all "Strapping bundles of Finnish ferocity", meet grisly ends several chapters in. They fight and fall in swamps and pine forests, coming up against tanks and cannon and the unfriendly fire of snipers and rival machine-gunners. In doing so, "The strong grew stronger; the weak faltered further under the strain." As the slaughter intensifies "No man was excused from his butchering duties."

Linna's soldiers have names and scraps of personality, but they are essentially "unknown" because of their sheer number. Some stand out due to their dialect, at times more Kentucky than Karelia: "Hot diggity! These are some dandy felt books I got me back there on'nat service road." However, most don't stick around long enough to make an impression on the reader. In the end, we give up remembering who's who, having long since come to the conclusion that Linna's aim is not to home in on individual plights and agendas but to show the whole great shapeless mass of a platoon, one that is continuously besieged and pared down. The brutality of the mechanical depletion of old-guard troops is offset by the belt-fed replenishment of fresh-faced new recruits. In the novel's final stretch, with their flanks even more exposed and morale in tatters, we witness Linna's ragged unit bowed by hunger, contemplating desertion, then bombarded by ground-attack planes. "This isn't a war," one man declares. "This is just horror after horror."

Unknown Soldiers still has the power to shock. Linna's men fight a dirty, dog-eat-dog war. By focusing on hardship rather than heroics, and eschewing any trace of gallows humour or lyricism, Linna's gutsy, visceral portrayal of war owes more to Mailer than, say, Waugh or Heller. In one memorable, if harrowing scene, a soldier left for dead beseeches overhead fighter planes to put him out of his misery. And then there is Linna's gimlet-eyed detail: a corpse on a stretcher, its dangling arm culminating in a clenched fist; bodies strewn on the ground, "many with their pockets already flipped inside out".

The relentless carnage will make some readers long for armistice and defeat. In places it feels as if Linna set out to depict a war of attrition that would simultaneously grind down his reader. And yet those who last the arduous course will find much to admire in Linna's unsparing prose and gritty realism. Not a comforting novel by many means, but a profound and enriching one.