By just about every theatrical yardstick, the Royal Shakespeare Company's production of "The Life and Adventures of Nicholas Nickleby," imported from London for a 14-week engagement here, is a prodigious experience.

The two-part script, adapted from Charles Dickens' 1837 novel, runs 8 1/2 hours, making it the longest play ever presented on the Broadway stage. With a company of 42 portraying literally hundreds of roles and 13 musicians contributing incidental music, it does not have a cast so much as a population.

The set, a jangle of wrought iron scaffolding and catwalks, invades the diminutive Plymouth Theatre. The costumes and wigs are so abundant that the crew has had to appropriate the basement of the adjoining Broadhurst Theatre.

Such statistics are the stuff of the "Guinness Book of World Records," but they tell only part of the story. In its epic sweep across England in the first half of the 19th century, "Nicholas Nickleby" captures more of humanity's disparate emotions, more of poverty's snaggletoothed wretchedness and more of youth's clear-eyed idealism than a season's worth of dramas. It is a teeming wonder.

On this side of the Atlantic, Dickens has largely been sentimentalized over the years. "A Christmas Carol" is matter for greeting cards, and "Oliver" plays in all our dinner theaters. The fierce social critic, who excoriated men of money and the manipulators of the Industrial Revolution has long since been supplanted in our minds by the painter of quaint Victorian scenes. And yet Dickens had a very dark view of the world and its deformations, and this production revels in them.

The events come in a headlong tumble that cuts across the full spectrum of society, as Nicholas (Roger Rees), his sister, Kate (Emily Richard), and their recently widowed mother (Priscilla Morgan) make their way to London, where they hope to start life anew. Nicholas is soon dispatched to a country academy run by the notorious Mr. Squeers (Alun Armstrong), who alternately starves and canes his charges in the name of higher education. There Nicholas befriends a deformed imbecile, Smike (played with ineffable sweetness by David Threlfall), before circumstances set the two of them on the road again. Meanwhile, Kate is suffering humiliations of her own in a succession of genteel jobs in London and finding her virtue under increasing attack. Hovering over brother and sister is the shadow of their uncle (John Woodvine), a sinister money lender who would sell his kin up the river if it augmented the figures in his ledgers.

The marathon script, adapted by David Edgar, has not omitted a single crucial episode from Dickens' novel (902 pages in the yellowed edition I read this summer). More important, it is ruthlessly faithful to Dickens' tone. Grays, blacks and whites are the predominant colors on stage, and the actors' faces are invariably distorted by grimaces of pain and anger. If there are also great waves of humor to the evening, it is the kind of humor that springs from the inalterable vanity of men strutting their stuff.

Part One, in fact, concludes on a riotous note. Buffeted by circumstance and wicked men, Nicholas has taken temporary refuge in the bosom of a provincial acting company, made up of drunks, hams, and a 19th-century version of Baby June, dubbed the "infant phenomenon." The straggling troupe's version of "Romeo and Juliet" is, of course, a delectation of histrionic pomposity and potion-defying resurrections. But Trevor Nunn and John Caird intend for this show-within-the-show to be more than a rousing crowd-pleaser. It is an image of the very absurdity that governs Nicholas' peregrinations in search of justice, just as it governs all men's affairs. The Royal Shakespeare Company, don't forget, is the company that gave us "Marat/Sade" and the folly that exploded in that piece lurks in every crevice of "Nicholas Nickleby."

Everything about this production carries a radical tinge -- its length, its underlying fury and the corrosive accuracy of the acting. Morality may triumph in the end, but that is convention's due. The true story -- humanity's perversity and self interest -- has no ending.

Dickens wrote "Nicholas Nickleby" as a serial, and it has all the sudden changes of fortune, the miraculous coincidences, the intercepted letters and the overheard conversations characteristic of the genre. Summarized, the events defy belief. Acted, they command it.

It is a measure of the adroitness of the performers that only by consulting the program afterward do you realize, for example, that Mr. Crummles, the generous provincial thespian and peacock, and Walter Bray, a sad, gray gentleman who seems to have melted into his wheelchair, are played by the same actor (Christopher Benjamin). Lila Kaye suggests a virtual thunderstorm as Mrs. Squeers, headmistress and scourge of schoolboys, yet she also plows across the stage in full majesty, a frigate at a regatta as Mrs. Crummles, erstwhile grand dame of the theater. The transformations are amazing. They make for a glorious gallery. The danger, if there ever was one, is that "Nicholas Nickleby" could have been nothing more than a continuous sideshow. But Roger Rees' performance as Nicholas keeps everything in perspective. With his angry shock of jet-black hair and an inbred sense of indignation that informs his every movement, Rees is the moral center in a world that has misplaced its morality.

As a result, the directors can spring some surprising metamorphoses on us without risk of upstaging themselves. Hat boxes and luggage piled high become a coach rumbling over the countryside. A bolt of lustrous black cloth is a rearing stallion. A dapple of light thrown on the wood floor conjures up a country churchyard.

And when Ralph Nickleby hangs himself in remorse, a stark spotlight floods his face and a dummy falls from the rafters, plummeting through a trap door in the stage with the clank and whoosh of an infernal machine.

"Nicholas Nickleby" leaves an audience exhilarated and spent. There is no discounting its length (its two parts can be seen on subsequent evenings for those who do not have the endurance for a single sitting). But I am not sure that a production of this scope and imagination doesn't end up by establishing its own rules, rules that have nothing to do with Broadway's usual desire to deposit an audience on the sidewalk in a state of falsely induced euphoria by 11 p.m. With uncommon audacity, "Nicholas Nickleby" not only takes on Dickens' sprawling novel, it fractures all the petty limitations we have imposed upon the stage as well. It is a show unto itself. A landmark.

"Nicholas Nickleby," by Charles Dickens; adapted by David Edgar; directed by Trevor Nunn and John Caird; sets, John Napier and Dermot Hayes; costumes, John Napier; lighting, David Hersey; music, Stephen Oliver. With members of the Royal Shakespeare Company.

At the Plymouth Theatre in New York until Jan. 3.