‘The Oatmeal Ark’ is a truly astonishing performance. The scale of the tale it tells, like the scale of its aspirations, is vast, and it has three grand themes so compelling that, even at parts of the narrative I did not much like, I felt perfectly unable to skip a single word. The first is a theme of contemporary travel. The second is an exploration of family history. The third is nothing less than a contemplation of the rise and decline of nations, of cultures, and even of ideas.

As a travel book in the widest sense –- incorporating, that is to say, geographical narrative, historical allusion and personal interpretation -– it seems to me unique. The happily unheroic hero of the book is its narrator, Beagan Gillean (whom I take to be a sort of fictional shadow of the author). This young man, having been led to suppose that he is the hereditary owner of an island off Vancouver, sets out to follow the emigration route of his forebears from the Western Isles of Scotland to the eastern isles of British Columbia, and he does it, as they did, almost entirely by water – slap across the Atlantic, through the myriad lakes and waterways of the immense Canadian hinterland, over the watershed of the Rocky Mountains and down the Fraser River to the Pacific.

It is a prodigious journey that he makes –- much of it done in canoes or inflatables -– and more than any other book I have read about Canada, this one resonates with romance. Romance and Canada do not often go together, at least in books, but for the character Gillean, as for the author Maclean, it is still a place of terrific suggestive excitement. Great learning has gone into this account of an adventure, great descriptive power too, and I found myself following its course with eager expectation, surrounded on my desk, and in my bed, by maps of Nova Scotia, Quebec, Ontario, Manitoba, Alberta and British Columbia – the vast slice of a continent through which the book takes us. Even its place-names are thrilling – Lake of the Woods, Thunder Bay, Quetico, Grand Rapids – and The Oatmeal Ark quivers with its intrinsic emotions, the loneliness, the bafflement, the sense of grandeur, the hope, as we travel from the Atlantic to the Pacific shore, now shivering with the cold of it, now plunging into deep still forest pools, now drinking beer with longshoremen or layabouts or Micmac Indians.

Or with ghosts, for throughout the book the fantastical chimes in. It is not to my own taste, but Maclean manages it without a falter. It is his conceit that with the contemporary Beagan, as with us, there travel several dead representatives of the Gillean family, from four generations. They speak in a different type-face from the rest of the page, and one purpose of their presence is to remind us of the conditions of the journey as it was in their own times, from the early 19th century to the dawn of the 21st. So we travel, so to speak, sometimes in bark canoes like the old voyageurs, sometimes in posh motor-cruisers like contemporary entrepreneurs, and we survey the passing Canada through eyes of the past as of the present.

But a more important function of the phantoms is to illustrate the changing values, outlooks and aspirations of a family, from Presbyterian piety to contemporary materialism -– and to emphasize, too, the power of continuity. These half-dozen characters are all recognizably Gilleans, all recognizably, though in different degrees of intensity, Scottish-Canadians. We watch a nation developing through their presence, we see the evolution of that quintessentially Canadian conception, multi-culturalism, and sadly we see the diminution of the people who were there all the time, the 800 original tribes of Canada.

Which brings us at the end of the book to the Pacific shore, where the Canada of our own time is hardly the Canada that the stout Scottish Gilleans have imagined down the generations. It is a hushed kind of conclusion, but not the high-flown challenging hush of the wilderness we have crossed. The land of the trappers and the voyageurs, the explorers and the Arctic aviators, of the storm-tossed Atlantic corvettes, the frozen north and the St Lawrence Seaway; the land of the unimaginable spaces is generally thought nowadays, and all too often by its own people, to be a bit of a bore.

This remarkable work reflects a very different reputation – and truth, too. If while you read it you are ever tempted to skip, as I sometimes was, resist the temptation. Its whole is majestically greater than its parts! I finished The Oatmeal Ark feeling that every word of it was true, that every word counted, and I even believed in the presence of those ghosts when, as they fluttered back into the empyrean (for they apparently had wings), the young Beagan concludes from his experience that words and water, love and reconciliation are the true eternals.

‘The Oatmeal Ark’ is republished by Tauris Parke in 2008. It was first published by HarperCollins UK and Canada in 1997.