From David Bowie’s sound, a writer’s vision for a song-by-song opus

Chris O’Leary at his home in Easthampton.Lane Turner/Globe Staff

EASTHAMPTON — Chris O’Leary saw David Bowie perform just the one time, at the Hartford Civic Center. It was the summer of 1990. O’Leary was a high school student in Connecticut. Bowie was in the middle of his international Sound+Vision tour, which was billed as a last hurrah for his vast catalog of hits.

It was a good show, but then again, so was the Rush concert O’Leary caught around the same time. To the future writer, Bowie was just another tile in the big mosaic of classic rock. A dazzling, prismatic tile, to be sure, but still.

So it’s as surprising to O’Leary as anyone that his life has come to revolve around Bowie’s music. After graduating from Boston University (where he dabbled in film criticism), he began working as a writer and editor for trade journals. To indulge his art-appreciation side, for a few years he blogged about music, covering specific years in American pop history. Switching gears, he chose Bowie as his new subject not because he felt like an expert or a completist on the man, but because he didn’t.

That is no longer the case. With the determination of an ultra-marathoner, O’Leary has written essays for every recording Bowie ever made. In early February, he will publish the second of his two-volume opus. At more than 700 pages, “Ashes to Ashes: The Songs of David Bowie, 1976-2016” (Repeater Books) is a jumbo sequel to 2015’s “Rebel Rebel,” which covered Bowie’s arrival from his first recording in 1964 (as Davie Jones) to the “Golden Years” of his mid-’70s breakthrough in America. “Ashes to Ashes” spans the 40 years from “Low” to “Blackstar.”

At 46, living with Lucy, his aging terrier, in a modest home in Easthampton, still earning his living editing white papers and writing about the legal and financial worlds, O’Leary could call himself the world’s foremost authority on the most enigmatic recording artist of our time. But he probably wouldn’t.

“I guess that’s always been my thing,” he says, sitting under a strand of Christmas lights in the living room where he keeps his books and records. “I’m the person not quite of the scene I write about.”

For O’Leary, Bowie fit a need. He wanted a research subject with longevity, an artist who’d explored various styles and muses. The Who’s Pete Townshend was on his shortlist, he says. He briefly considered Neil Young.

But Bowie, who would have turned 72 next Tuesday — he died on Jan. 10, 2016, two days after his birthday — was the ultimate transformer. Whether you’re a fan of his glam-era Ziggy Stardust persona or the big ‘80s pop of “Let’s Dance,” or if you loved his take on “Nature Boy” for the “Moulin Rouge” soundtrack, over the eventful course of his half-century career Bowie gave the world total access to his creative mind. As it happens, he provided one of his admirers with the project of a lifetime.

What began as a “writing exercise,” as O’Leary acknowledges at the outset of “Ashes to Ashes,” soon grew into an epic amalgam of logbook details, liner-notes minutiae, contextual analysis, critical commentary, and, occasionally, pure poetry.

“David Bowie today is a language,” O’Leary writes, “a set of precepts and responses, a code that anyone with requisite amounts of style, guts, shamelessness, and weirdness can access.”

Bowie’s own insatiable appetite for ideas — if you haven’t already, do seek out his list of 100 favorite books — supplied O’Leary with a bonanza of material. Musically, “Ashes to Ashes” spans the artist’s infatuations with the city of Berlin, the MTV era, electronic drum and bass, and art song. Lyrically, the range of his inspirations is astounding. A single page of O’Leary’s book includes references to Walt Whitman, George Orwell, and “The Cabinet of Dr. Caligari.”

Bowie had effectively retired from the public eye when O’Leary launched his blog in 2009. For a time, it appeared to O’Leary that his blog, which he’d named “Pushing Ahead of the Dame” (a line from Bowie’s song “Queen Bitch”), would have to end with a satirical song. Bowie had come out of reclusion to serenade Ricky Gervais as “the little fat man” in an episode of the comedian’s mid-2000s HBO series “Extras.”

Then Bowie stunned the world with his unannounced pair of “comeback” albums, “The Next Day” (2013) and the masterful “Blackstar” (released on his 69th birthday in 2016). These coincided with the world tour of the museum exhibit “David Bowie Is” and the stage production of Bowie’s musical “Lazarus,” which starred Michael C. Hall. O’Leary saw the show twice.

Bowie was fighting cancer as he worked on his last songs, though only a few intimates knew. The cast album for “Lazarus” was recorded a day after his death.

“That’s a story I’d love to read,” says O’Leary. “They did ‘Lazarus’ every night for two weeks after he died. Those must have been incredibly emotional performances. They were just doing a job, and suddenly they’re on the frontlines, consoling people.”

The collective grief over Bowie’s death, he writes, “may be among the last unified moments in global civilization.” On the anniversaries of Bowie’s birth and death, O’Leary’s interpretations of Bowie give us another chance to pay tribute.

For his next act, he’s thinking about Talking Heads, and how that band’s career arc aligned with the gentrification of New York. For now, though, he says, “I feel like this is my last word.”

Bowie reportedly left behind five unheard demos. O’Leary wraps his project by asking whether they should see the light of day. He says no.

“Let this be our gift to the future,” he writes. “There will never be a last David Bowie song if there are always five more to come. The end of the David Bowie story is that it doesn’t end . . . May he forever keep pushing ahead.”