Consider the tightrope walker. See him up there, a tiny stick figure etched against the city skyline, treading a cable strung between the two unfinished towers of the World Trade Center.

What is he—an artist? A lunatic? A rebel? Maybe all, and maybe more.

Far beneath him, a great city in the throes of a revolution that no one, in 1974, really understands.

Wracked by Watergate, ravaged by Vietnam, with its ghettoes burning and the first hints of the Internet beginning to buzz across the globe, America is emerging from its post-war slumber and will never sleep as peacefully again.

And on a smaller scale, see the many lives. The hooker. The city judge. The Park Avenue matron. The Irish-immigrant priest.

Every life in its own diorama, each person lost in the web of his or her own troubles and joys.

Sometimes the lives intersect — the city judge arraigns the tightrope walker, the priest ministers to the hookers — and sometimes they remain apart, but together they form a mosaic as painful as it is beautiful.

This is the universe that Colum McCann creates, brilliantly, in “Let the Great World Spin.” The Irish author — like the tightrope walker that is his novel’s leitmotif — finds his truest and best footing in this, his fifth novel.

“Sometimes,” says his Gloria, a descendant of slaves who has made her heartrending way from rural Missouri to Syracuse University on scholarship, only to find herself on the 11th floor of a nightmarish Bronx housing project, “you’ve got to go up to a very high floor to see what the past has done to the present.”

That’s what McCann does for us.

His literary tightrope act is a showoffy, scene-stealing spectacle that’s hard to tear your eyes away from. He takes chances, dancing on the wire of a plot that starts in Ireland, moves to New York, and ends as stunningly as any novel I can remember.

If you believe in redemption, or would like to, the novel’s climax — a life-changing moment outside that housing project — should be an enduring point of reference, and an inspiration. Let’s say only this much: It involves a rich woman, a poor woman, and the fates of two little girls whose futures teeter precariously on the line between promise and disaster.

How does change happen? It happens by the grace of God, though McCann may not give it that name.

Always moving from high to low and back again —from global to personal, highwire to street, penthouse to project — McCann’s vision helps us see. And to make some sense of it, too, as much crazy, wondrous sense as it made for Phillipe Petit (the novel’s only “real” character) to traverse his self-made span on August 7, 1974.

The story begins in Ireland with two boys, bunk-bed brothers, who eventually come to America.

And, although “Let the Great World Spin” is a New York City novel in the time-honored tradition, it also has a serious case of the Irish blues — the fatalistic world view, the melancholy depths in which every joy has sorrow close behind: whisky neat with a heartbreak chaser.

If William Butler Yeats and Allen Ginsberg had written a novel together, it would be this sad, this deep, this urban, this manic and this highly charged. This spiritual.

McCann’s is not a happy vision of humanity, but it is a hopeful one. As Dave Eggers, after an early look at “Let the Great World Spin,” observed: “Leave it to an Irishman to write one of the greatest-ever novels about New York.”

Those Irish brothers, compelling as they are, are quickly joined by character after character in this richly layered tale. Joining and separating, changing each other’s lives in love and war and death, each could be (and somehow is) its own short story. McCann has no shortage of imagination.

Six pages before the novel’s end, he’s still introducing a new character — the artist/wife of one of the original brothers, back in Ireland, now many decades later. He sketches her memorably: “There was something of the beautiful failure about her.”

The novel overflows; it expands; it teems. It is, at times, excessive. Enough, already! We are drowning in these overlapping, intensely felt lives. But that’s like complaining about a feast. If it’s too much, walk away.

Ah, but that, it turns out, is impossible. McCann’s power — his language, his human understanding, his vision—holds us in an embrace as encompassing as the great world itself.

Margaret Sullivan is the editor of The News.

FICTION

Let the Great World Spin

By Colum McCann

Random House

349 pages, $25