Does one of the salient works of the black children’s lit breakthrough still hold its own? Is it still the knockout that I pronounced it, at Kirkus, in 1971?

The Planet of Junior Brown was Virginia Hamilton’s fourth book — each of them different from the others, and from anything else around.

Hamilton, an emerging black children’s writer, was finding her way in turbulent times. Civil rights clashes in the South and civil rights demonstrations in the North dominated the public discourse. Children’s books about black life, most of them by white writers, were overwhelmingly stories of prejudice countered and discrimination overcome.

Hamilton had another outlook. She’d grown up on the family farm in Yellow Springs, Ohio, with a storytelling grandmother and an Underground Railroad legacy. As a student at Antioch College, close by, she’d been privy to the progressive educational views and abolitionist idealism of Horace Mann, the school’s first president. Although her immediate world wasn’t free of unfairness, she had other things to write about besides racial conflict.

It also helped that Zeely (1966), her striking debut novel, originated as a short story for a college writing class, not as a children’s book. No presuppositions were in play. Young Geeder (née Elizabeth), awestruck by her statuesque neighbor Zeely, a keeper of pigs, imagines her a Watutsi queen like the one in an old magazine. Ridiculous? Not to Zeely, who had once told herself just such stories, and not to readers newly exposed to the range of African cultures in the daily news and the media at large.

The House of Dies Drear (1968) qualifies as a mystery: a present-day family moves into a house in Ohio that was once a station on the Underground Railroad…where nothing is quite as it seems.

In Time-Ago Tales of Jahdu (1969), the first of Hamilton’s folk-infused writings, young Lee Edward takes inspiration from the four linked hero tales that end in “a fine, good place called Harlem.”

Hamilton had meanwhile moved to New York, married aspiring poet Arnold Adoff, and become the mother of two children. On the national scene, new words and phrases — black, Afro-American — had entered everyday speech; new images of black beauty and black power were permeating the lives of children. For black children, the changes could be monumental.

The Planet of Junior Brown (1971), set firmly in Manhattan, is a mixture of social realism, psychodrama, and utopian fantasy. An original. What it isn’t is time-bound or topical. Big things happen here. “Strong substance in a juvenile novel,” I wrote in 1971.

Big characters appear, too — outliers, most of them.

Hidden away in the basement of a New York school is a model of the solar system with a new, tenth planet, the planet of Junior Brown — constructed by Mr. Pool the janitor, a lapsed math-and-science teacher, and his accomplice, renegade eighth-grader Buddy Clark, for the benefit of Buddy’s troubled classmate Junior Brown: hugely talented, monstrously fat, riven. A “sad, fat boy.”

Yes, the story revolves around Junior Brown — how to free him from the delusions of his manic music teacher, how to loosen the strictures of his smothering, asthmatic mother.

But it’s Buddy Clark, a homeless boy at home in the world at twelve or thirteen, who turns the wheels, this way and that. At Mrs. Brown’s groaning dinner table, Buddy coolly opts for a meatless meal. With his college-grad boss at the newsstand, he discusses magazine covers and the meaning of irony. In the office of the sympathetic assistant principal, he embeds his and Junior’s truancy in a web of hard-luck stories.

He is most fully engaged, though, on his own planet — one of a network of underground refuges for homeless boys, in basements and backrooms, maintained by somewhat older boys, veterans of the streets, like Buddy.

The logistics of concealing and supplying the hideaway, of keeping the younger boys fed and clothed, of seeing them off to school and to honest work, make a taut urban survival story. The psycho-dynamics of steering them away from a life of escalating crime is of another order of involvement: moral and ethical.

In a quiet, powerful scene, two boys wait for Buddy at his planet: savvy “Franklin Moore” and a smaller, younger boy, fearful of the dark, who has yet to choose his homeless name. (“Just having a last name the same as the mama or daddy you once knew reminds you of them,” Buddy tells him. “And remembering is going to make you feel pretty bad sometimes…”) Loosened up and warmed up by a spartan banquet, the boy firmly announces he’ll be “Nightman.” Nightman who? “Nightman Black.”

Franklin, suspicious and hostile, is the real problem. In his pockets, his shirt, his socks, Buddy finds expensive watches, rings, and other valuables, plus a leather wallet. “You ain’t nothing but a thief,…a wet-bottomed little hustler.” Taking twenty-five dollars from the wallet (which he’ll mail to the owner), he gives Franklin five dollars to keep Nightman and himself for a few days, “until Monday when I get paid.” The other twenty will be for other homeless kids.

Nightman demurs. “I want you to put back the five dollars you give to Franklin.” He’ll get by with an apple or an orange and a roll, things he can cadge, until Buddy provides dinner. Reluctantly, Franklin complies. What about the other twenty dollars? “I think,” says Nightman, “you better keep it for the others.” Sitting with his legs folded in front of him, a hand on each knee, Nightman lacks only a throne to look “like a king.”

For Buddy Clark, Junior Brown is a special case, a special person. He has food, clothing, and shelter in abundance, even overabundance. But what he wants most — his music — is denied him. The grand piano of his teacher, Miss Peebles, is off-limits due to a malevolent (imaginary) relative. Worse, his own upright has been emasculated to spare his mother the sound. The wires have been removed, Buddy sees, though the felt hammers are in place. “But the hammers struck against nothing. As Junior played on and on, the hammers rose and fell soundlessly.”

Taking away his music. “How could she do that to her own son?” Buddy thinks.

In the upshot, Mr. Pool is forced to take down the solar system and vacate the basement hideaway; Junior Brown runs away from home to lure away Miss Peeble’s malevolent relative; and all concerned take refuge in Buddy Clark’s planet-of-the-homeless, which will henceforth be known as the Planet of Junior Brown. A piano may even be hoisted in.

All told, a bit much. Preposterous, even. “This is not a story to be judged on grounds of probability,” I wrote in the original review, “but one which makes its own insistent reality.”

*    *    *

Regardless, today’s kids aren’t buying it. The Planet of Junior Brown was a 1972 Newbery Honor Book, which keeps a certain number of copies on library shelves. But that’s apparently where most of them remain. Of twelve copies in the New York Public Library system in late September 2014, ten were available. Brooklyn had thirty-five of thirty-nine copies on hand; Boston could produce seventeen of nineteen. In some cities with very small holdings, every copy was in. New York City school libraries, too, report meager circulation for years.

Why? There are structural impediments, certainly. The opening chapter, where Buddy and Mr. Pool put the finishing touches on the solar system, is something of an astronomy tutorial. The chapters are long from the outset, moreover, and grow still longer — from twenty or so pages to forty or so — without distinct narrative breaks. By today’s standards, it’s a demanding book to read.

But Hamilton, a librarian colleague reminds me, was always a “hard sell.”

What’s different is the spirit of the time, the zeitgeist. The book’s core values — individual responsibility and mutual assistance — have no expiration date. But in The Planet of Junior Brown they are in service of a greater good: the transformation of society as a whole.

We thought big, in the late 1960s and early 1970s, and children’s books, too, had their sights on the stars. Mr. Pool’s belief that “the human race [was] yet to come” and that his boys were “forerunners” did not strike me as outlandish when I wrote the original review. Rereading the book recently, the visionary element faded in the stronger, clearer light of the boys’ actual bonding.

At a guess, the human drama will prevail and Junior Brown will continue to find susceptible readers, here and there, to whom it will mean a great deal. If you care about the story, and the kids in it, you also understand why Mr. Pool endowed them with heroic powers. The aftereffect, in any period, is inspirational.