Maurice Sendak used to tantalize interviewers with the story of his first unpublished book. It told of a love affair between a brother and a sister that culminated in a shocking hospital scene. The little girl bursts into the room where her heavily-bandaged brother is recuperating from an accident. The siblings embrace passionately and shout “we are inseparable!” Before the adults can pull them apart, the children leap out of the window and fall fourteen stories to their deaths.

Maurice, aged seven, drew the illustrations for “They Were Inseparable,” and his brother Jack, who was twelve, composed the text. The book was dedicated to their sixteen-year-old sister with whom they were both infatuated. Sendak’s first critics, his older relatives, applauded the story and urged the boys to perform it at family gatherings.

When I interviewed Sendak a few years ago, I asked him if he’d ever considered reworking “They Were Inseparable” and publishing it. He laughed. “Oh, believe me, I’ve thought about doing it,” he told me. “You know, just to piss people off. But I’m afraid ‘They Were Inseparable’ shall remain unpublished until further notice.” I had forgotten about this exchange until I encountered Sendak’s newly-published, posthumous “My Brother’s Book.” He had struggled with the title for this story. He might as well have called it “They Were Inseparable.”

It opens “on a bleak midwinter’s night” when a raging fireball scorches the sky and slams into the world: a meteor hit. (It seems that whoever is responsible for sending meteors to earth is a Sendak fan—the recent cosmic event over Siberia helped mark the book’s publication). The shattering force of the fallen star sends two brothers reeling to opposite ends of the earth. Jack is catapulted to a polar region where he is encased in ice. Meanwhile, Guy spirals around “in the steep air” until he alights on a verdant land—and, in a comically timed jump-cut, ends up in the mouth of a giant bear. The wild thing’s mouth turns out to be a portal to a sinuous and dewy netherworld where time re-spools itself, and in which you simultaneously rise and fall—which is to say, you dissolve—and through which Guy, like so many other Sendak heroes, drifts and tumbles and morphs, until finally gravity is restored and there is nothing left to do but rest. He finds himself in the arms of his beloved lost brother—a substitute for the cozy bed that appears at the end of other Sendak books—and they share an earth-bound sleep. The fissure at the beginning of this tale isn’t of the domestic but rather of the cosmic sort, and so its unfolding is more associative and dreamlike than the usual Sendak tale. This isn’t about home as house, it’s about home as earthly existence.

Sendak must have done something right, because some reviewers seem baffled. Ellen Handler Spitz, writing in The New Republic, dismisses “My Brother’s Book” as a work that isn’t a masterpiece and therefore would have been better left unpublished. Its main function is to remind the disinterested specialist that it’s finally time to examine Sendak’s body of work through the “lens” of his sexuality. (When I was a child, Sendak’s sexuality was certainly critical to my understanding of these stories). On its own terms, this new story, she argues, is “emotionally distant” and “unintelligible.” It’s hard not to recall the notorious comment made by a reviewer in Publishers Weekly that “Where the Wild Things Are” was a “pointless and confusing story.”

It’s true that “My Brother’s Book” doesn’t have the burnished, poster-like bravado of Sendak’s best-known works. It’s also true that it isn’t trying to. The pictures in “My Brother’s Work” are not designed for the wide-eyed (though it is somehow comforting to know that Sendak, up until the end, was still better at, or just more interested in, drawing paws than feet). These are compressed images, framed on the page by a good deal of white space. Because this is a book intended for adults, Sendak asks his reader to look patiently into the layered watercolors. The seeker is rewarded with a lavish and delicately applied palette: a grand finale of streaming and dappled color, from thundercloud blues to lollipop yellows. The effect is of looking deep into a microscope and entering the dramas of an animal cell, the pulsing textures and musical logic, the way each tiny organelle busily plays its part in sustaining the general tremble of the thing.

William Blake’s influence has occasionally peeked out of Sendak’s books. In “My Brother’s Book” we see a more complete Blake-scape. The homage starts with the first image: Like Blake’s William—from his illustrated poem “Milton”—we see Jack dramatically impaled by a falling star. Sendak is playing with Blakean themes and formal elements: the pictures framed by white space; the watered-out blues and pinks and blacks; the dark outlines; the theatrical gestures; the downward flooding lines; the heroic nudes, which Sendak, as usual, seems to knead from dough; the falling star separating two brothers (in “Milton,” the falling star comes between William and a mirror-image named Robert, after Blake’s brother).

As with “Milton,” there is an unmistakable eroticism. In Blake’s image that exploding star is none other than John Milton himself, purified of his Puritanism and streaking back to earth to ravish the poet William Blake, a visual theme that becomes more explicit as that story develops. In “My Brother’s Book,” this theme is less insistent but it flits about from beginning to end. The brothers’ reunion is more like an organic union of bodies.

Tony Kushner, a close friend of Sendak’s, told me when I spoke to him last week that this book is a farewell to Eugene Glynn, Sendak’s partner of over fifty years. “Jack is Jack,” he said. “Guy is Gene. He was really saying goodbye to both. And also, in many ways, to himself.”

Perhaps just as important as these goodbyes is Sendak’s farewell to Blake, and to all of his muses. Sendak had a heartfelt, almost reckless love of his artistic influences. How better to demonstrate Blake’s outsized influence on him than by opening the book with an allusion to Milton’s outsized influence on Blake?