A flurry of books marked the last half-dozen years of his life. Not everyone realised there were two authors producing a stream of material; there was a Scottish writer of great talent who called himself "Lewis Grassic Gibbon", a thin disguise of his mother's maiden name; there was a professional journalist and critic called "J. Leslie Mitchell" who kept an independent output of material just as professional, just as well written, but drawn from very different sources.

Mitchell believed wholeheartedly in the diffusionist theory that civilisation was a blight slowly strangling the native goodness and ability of human kind, the Depression simply the last gasp of a corrupt system, and that revolution and the shaking-off of Church and State, Government and class was the only way forward. A Marxist and an anarchist, Mitchell would have welcomed revolution, though as a writer he also faced a plangent nostalgia for a Scotland which he had known in youth, and watched destroyed by the First World War which changed the Mearns beyond recognition.

The themes of his work are clearly set. On the one hand, he produced autobiographical writing which celebrated that Scotland, Stained radiance, The Thirteenth disciple, an unfinished novel The Speak of the Mearns and - unforgettably - Sunset song in which he shows his thinly-disguised autobiographical self (cleverly re-cast as a female protagonist, Chris, who run through the trilogy as a binding thread) watching the sunset of an age, while singing its beauty as well as the harshness of the tough farming conditions of his childhood experience.

In the first part of the trilogy we read about the author's childhood years, small farms, tight communities, harvest, spring, weddings, funerals - a Scotland easy to love, but never veering to kailyard or sentiment, since the other side is never far away, grinding repetitive work, gossip, spite. But the sunset comes with War, with the killing-off of the finest in the community, the dreadful stripping of the trees without which the old farming is effectively killed off.

The rest of the trilogy carries the story forward, away from nostalgia and times past, to a Scotland of here and now, industrial Scotland, smallish towns, finally the city (Aberdeen) in the Depression years, grey, hopeless, sometimes violent - a diffusionist's nightmare of the human spirit ground down. But it is a brave modern Scottish classic, turning away from easy temptations to romanticise Scotland, and facing up to the consequences of change. It was published in 1934, just before the author's death, and it was fully up to date.

Oddly enough, though much of the rest of his output was fantasy (highly successful science fiction, Three go back and Gay Hunter) it was firmly up to date too: Mitchell wrote about societies without the blight of civilisation, trying to show that human beings had once been free, could be again. Wonderfully successful short stories about the Scottish countryside make the same point again and again. Paradoxically, the author himself had to break free - to Welwyn Garden City, in Hertfordshire - to gain the freedom to see Scotland clearly. But when he did, he re-Created the past, and sharpened the present, more successfully than any other writer of the century.

Part of the success lies in the use of language, innovative and very much open to first time readers. Without a strong covering of phonetic Scots, Mitchell writes in what looks like effortless English, though a lot of what is written can be read out aloud as Scots, many of the words disguised as common English words, though recognisable to a Scot for what they are. It is a non-threatening style, lyrical, musical, and it has done much to explain the success of his work.

Television brought him to a new audience of millions, in North America as well as in Britain. He is widely taught in school and university. His Scotland is bitter-sweet, a place where real people live, and work, and die. It is not a Scotland of misty past, but a Scotland of sharp-edged present, with a respect for the past which does not sentimentalise or take refuge in a vanished countryside.

James Leslie Mitchell was to have a short success. Republished in the USA, he was rapidly growing in reputation when peritonitis carried him off suddenly in early 1935, at the threshold of what seemed likely to be a very successful career. His close friend Hugh MacDiarmid co-operated with him in Scottish scene (1934), a jointly-authored squib in which they lambasted what was wrong with their country. In its savage attacks on people, institutions and cities (Mitchell on Glasgow and Aberdeen is unforgettable) it is elegant, witty, timely. It was a major loss to Scottish writing when Mitchell died, and thirty years of eclipse were to follow before the recent revival and - most important - republication which is again making available one of Scotland's most important modern authors.