EVERY GRATEFUL READER who was exposed to Mark Helprin's recent collection, Ellis Island and Other Stories, knew that a fresh voice and vision was on the march. Although the author had brought out two previous books that signaled the gathering of forces of a major talent, it was Ellis Island that brought him to the attention of his first real audience. His combination of the realistic and fantastic intertwining of experience, guided by compassion and a prose style as clear and shining as a northern star, gave hope on two levels: it opened up possibilities beyond realism for a transportation of life that could no longer be contained by the literal, and it gave almost therapeutic faith to those disillusioned and wearied by much serious fiction. Helprin was that rare thing, a first-rate technician who was also a sincere standard- bearer for a new dawn in humankind's endless effort to lift itself out of suffering and injustice.

Among the proud fictioneers of a new generation, Helprin stood alongside the late John Gardner as a messenger of mature optimism and an enemy of the depressing post-Beckett doom. Both offered inspiration which could be believed.

Helprin has now released the most ambitious work he has yet attempted, a huge cyclorama that covers a hundred years in time and at least an equal number of characters. It's theme is no less than the resurrection of New York from a city of the damned to a place of universal justice and hope. One motto that magically appears and reappears several times during the novel sums up the author's intention: "For what can be imagined more beautiful than the sight of a perfectly just city rejoicing alone?" Only Mark Helprin could present his utopian cause with such eloquent directness, and it would be a hard-hearted reviewer who didn't root for him to cleanse our cynicism and prepare us for this brave new world.

Unfortunately, Winter's Tale turns out to be a self- willed fairy tale that even on its own terms refuses to convince. The future that the author wants so beautifully to paint is more truly a nostalgic elegy for a late 19th-century city, when innocent young men and girls had their happiest moments ice-skating, eating "roasted oysters," sitting "by the hearth," driving in horse-drawn sleighs and the like. All the complexity of a 20th-century megalopolis is quaintly and sometimes cutely simplified so that Helprin can mythologize the simple virtues of our ancestors and make them goals of the future. None of the alienation, hostility, electronic bewilderment and minority aggressiveness of an actual New York is allowed to be heard. Even the scenes of brutality and poverty seem to be a stubbornly romanticized version of old New York etchings and photographs, with echoes of Stephen Crane and Dickens in the pictorial writing rather than the more challenging fragmentations of Hart Crane and John Dos Passos.

This kind of single-minded idealism, at the expense of the difficult real, is reflected in a plot which soars so complacently in every direction that ultimately one page reads like another. The central figure who is supposed to bind it all together is a noble burglar named Peter Lake, an almost Damon Runyon type with a heart of gold, except for the fact that he lives for a hundred years and spans the New York of Boss Tweed to that of Mayor Koch. Peter's great pal is a flying white stallion named Althansor. Together they escape from the dreaded Short Tails gang, rescue innocent maidens, defy the laws of gravity and even undergo a tear-jerking separation until they are reunited in death. But even death is only an illusion in Helprin's supreme fiction. Another motto in the book reminds us: "Remember, what we are trying to do in this life is shatter time and bring back the dead."

Nevertheless, while still alive in the mundane sense, both Peter Lake and Althansor introduce us to a vast collection of semi-real New York villains, dreamers and millionaires who bear such cuddlesome names as Pearly Soames, the Rev. Mootfowl, Humpstone John, Auriga Bootes, Juliet Paradise, Jesse Honey--you get the picture. Each is a "character" in the colloquial sense, and it would be less than fair to Helprin's obvious gift for drawing colorful oddballs to say that they aren't eye-catchers. They are, but since the author jerks them around like play things to suit his whims, our interest gets diluted and wary fairly quickly. Although this is a novel ostensibly concerned with the resurrection of souls from the veil of materialism--and the moral rebirth of a dying city--the emphasis on funny names, odd costumes and eccentric behavior often makes us feel that we are witnesses to a quaint vaudeville show. There is a split between the high spiritual ambition of the book and an old-fashioned need to hook the audience with external bizarreness, which soon becomes predictable.

Granting all these disappointments, one still must point out that Mark Helprin is no less a spectacular writer than before. Rare talent might be misused but it can't be lost. When he reaches the climax to his cloudsy fable, and New York is burning as preparation for the millennium, he could well be a new and unvulgar Cecil B. DeMille of prose as he engirds the city with words and shows his power with big effects. It takes a far-ranging eye to conceive such a spectacle. It takes an equally rich and uncommon imagination to take on a novel of this perilous scale and import. The writer who takes risks is always more admirable than the miser of small success.

But every indication is that this book should be a crucial intersection in Helprin's career thus far. He has choices to make, inner maps to consult. His refusal to make taut his fantasies with the electric shocks of a commonly understood reality--as in the past--has diffused and muffled the liberating punch of his vision. Worst of all, it made one formerly enchanted reader want to quit before the end.