There was nothing particularly enthralling about Wilfred Owen's early life.

He came from a rather dull lower middle-class background, he was frustrated by not being able to attend university, and he had typical relationships with his parents. His father "didn't really want a stay-indoors poet for a son" but his mother adored him: affection that Owen returned in abundance. As Guy Cuthbertson writes, "the apron strings were never cut - not even by the bullets of the Western Front".

Intellectually, Owen was conventional (he much preferred Keats and Tennyson to the modernist firebrands) and, beyond the realm of poetry, he retained somewhat juvenile tastes. Even his sexuality, much discussed these days, was probably less fascinating than we are sometimes led to believe. He appreciated male beauty and probably had homosexual desires, but he was really just one more young man trying to work out who he fancied.

All told, if he hadn't turned into one of the 20th-century's finest poets we would not have the slightest interest in him. But that is what he became, producing "sophisticated, inventive, courageous, original work" that manages to appeal to lofty critics, impatient school children and the general reading public in equal measure - a rare hat-trick.

Was it the war that made Owen a wonderful poet? Well, yes and no. As Cuthbertson explains, Owen is routinely portrayed "as some kind of fool who had thought war all flowers and japes until he arrived at the Western Front". On this analysis, he was shocked into greatness, but it is crucial to remember that his skills were already on display before the trenches were dug and that, whatever the world's geopolitical tides had in store, poetry would still have represented "the very crown of life and constituted its meaning". For all that, it was only the horrors of conflict that could inspire haunting descriptions of soldiers "bent double, like old beggars under sacks,/Knock-kneed, coughing like hags". War gave Owen a great deal, though, of course, he paid a dreadful price.

The crucial question, and here Cuthbertson's book becomes extremely useful, is what Owen truly thought about the war. He certainly did not rush to join up and would probably have preferred to dodge the whole affair, but this was hardly unusual. By the summer of 1915, 2.25 million British men of military age had volunteered: but five million had not yet done so. Owen despised the cruelty and squalor of warfare, but he was no kind of peacenik. Indeed, there were some aspects of being a soldier that he thoroughly enjoyed. Joining the officer class was a significant achievement for someone of his social station, and he was not displeased with the uniform and the riding crop that the Manchester Regiment provided.

Even that most famous and quoted of poems, Dulce et Decorum est, may not be quite what it seems. According to Cuthbertson, it is "not in fact a poem that accurately captures [Owen's] attitude to the war, and there was always something Horatian or Boys Own Paper about his outlook." One might ask, therefore, why he wrote it, but the very question assumes that poets always mean exactly what they write and always resist the temptation to swap authenticity for artistic licence. I'm not sure if I fully accept Cuthbertson's reading of the poem, but it gives one pause for thought.

None of this means that Owen didn't despise the suffering and futility of the Great War, but his outrage and compassion must be placed in context. He was not an anti-war campaigner, just a brilliant poet trapped between expectations and reality. Before joining the ranks, Owen confessed that "the war affects me less than it ought". When there was no escape from signing up, he thought a posting in Egypt (something of a pipedream) could be quite good fun. When he arrived at the Western Front ("more Roundhead than Cavalier now") the chivalric visions had to compete with the dirt, disease and devastation. Owen's only option was to put pen to paper, and thank God that he did. The least we owe him is to read his poems with subtlety. Cuthbertson helps us in this work.

Owen was, in so many ways, an unexceptional man. He never quite grew up, he was a snob without the social wherewithal to back his pretensions, and he had his curious moments: best of the bunch must be pretending to be the son of a baronet while teaching English at the Berlitz School in Bordeaux. And yet he was also the genius who wrote Strange Meeting: one of the greatest poems in the language.

This impressive biography shows us both aspects of the man and it sheds new light on important aspects of Owen's literary career. We should not, for instance, make too much of a cosy legend out of the relationship with Siegfried Sassoon. The pair enjoyed mutually enriching poetic encounters, but Sassoon always regarded himself as the senior partner and referred to Owen, condescendingly, as "an interesting little chap" who was "perceptibly provincial". Cuthbertson is also very good on the religious context of Owen's verse, especially the impact that French Roman Catholicism had on a man brought up in a somewhat humdrum variant of English Protestantism.

At least we can all agree that Philip Larkin did a very good job of summing up what made Owen's subjects significant: "If his verse did not cease to be valid in 1918, it is because these things continued, and the necessity for compassion with them." Owen died an unfeasibly unlucky death - within days of the end of the war. He will therefore always be that poor soldier dreaming of buying a little country house in Kent or Surrey where he could raise pigs and write peacetime verse. There is every chance that such verse would have been splendid and that Owen would have returned to a pleasingly uninteresting life.