Tim Murphy’s hugely ambitious new novel, “Christodora,” tackles the legacy and costs of AIDS and the activism that arose to meet it. At the heart of this rich, complicated story is Mateo, a gifted child whose mother has the disease and dies shortly after his birth. He’s adopted by two young artists, Milly and Jared, who bring him home to their East Village apartment building, the Christodora of Murphy’s title.

(Grove )

As the novel shifts back and forth across four decades, from the first reported cases of AIDS to an imagined New York City of 2021, Murphy offers a compelling portrait of the community of activists that transformed queer life in the 1980s and ’90s. Among them is Mateo’s mother, Ysabel, and the novel’s most compelling character, Hector Villanueva, a young scientist who leaves his job in the New York City Department of Health to join the radical activist group ACT UP.

Murphy is the author of two earlier novels, but he’s best known as a journalist, with two decades’ experience reporting on HIV/AIDS. His depictions of the day-to-day business of activists and bureaucrats have uncommon authority. He vividly captures the diversity and tensions within the AIDS movement: At an ACT UP meeting early in the novel, Hector divides the attendees into “white boys”; his fellow men of color, who refer to themselves as “Brown Town”; and lesbians who overlook ideological and gender differences to stand in solidarity with the afflicted.

Murphy illustrates lesser-known issues in the battle against AIDS, too, from the effort to gain recognition of woman-specific ailments to the splinter group of ACT UP that worked with the Clinton administration to develop and test the treatments that would eventually make HIV/AIDS a manageable disease.

The richness of Murphy’s account of AIDS activism lies less in the tragedy of meaningless death than in the exhilaration of purpose, the transformation of despair into a force for meaningful change. But the most moving sections of the book deal not with the height of the crisis but with its aftermath.

Murphy’s chapters leap, sometimes confusingly, between times and characters. We meet Mateo first as a reserved child happy with his adoptive parents; then as a cocky, rebellious teenager whose confidence is undercut by a “sense of being lost and wrong”; then as an addict, caught between remorse and need. Hector appears only in later chapters as a pillar of the activist community in the ’80s and ’90s. We first glimpse him as a looming, vaguely menacing neighbor in the Christodora, who “through the first decade of the 2000s . . . unraveled before the neighborhood’s eyes.”

Author Tim Murphy (Edwin Pabon)

Murphy’s novel is one of the few serious attempts I’ve encountered in literature to explore the crisis of meth addiction among gay men. Drug use inspires the finest writing in “Christodora,” and Murphy writes of addiction with sympathy and pathos.

For both Mateo and Hector, drugs promise a kind of restitution that nothing else in their lives can supply. “This is the perfect place,” Mateo thinks the first time he smokes heroin; the drug is “the hole in the air we crawl into to get there.”

More than a decade earlier, Hector recovers the “I-need-nothing-else-ever perfection” of his dead lover’s embrace in his first hit of crystal meth. “You just helped me figure out how I’m going to cope with the rest of my life,” he thinks of the casual sexual partner who introduces him to the drug.

What’s most devastating about this scene is that the trigger for Hector’s collapse isn’t his lover’s death but his own success in helping to develop effective treatments. No book has made me feel so intensely not just the ravages of AIDS but also the devastating cost of activism. The protease inhibitors that would make AIDS a manageable condition came too late for the thousands of men and women who died; for survivors, they took away a meaningful outlet for rage.

If Murphy’s decades as a journalist provide much of the novel’s richness, they also work occasionally to its detriment. Because of the book’s jumbled chronology, many chapters, especially early on, begin with a journalistic presentation of context, expository passages that often cover huge swaths of time in a fly-over narration that generates very little emotional heat. Attempts to incorporate these passages into the scene often make matters worse, requiring characters to lose themselves in reverie as they conveniently summarize their pasts; transitions between flashbacks and present action are too often baldly signposted with phrases like “he’d gone off on a tangent in his head.”

There can be something overly neat in the way the book’s narrative strands intersect, as when Jared and Milly’s first time having sex falls on the same day as — and is intercut with — Issy’s first ACT UP meeting. Nothing in “Christodora” is subtle, nothing is unstated. At times I found myself longing for a greater faith in the power of image or action to convey emotion and significance.

Even so, by the book’s overwhelmingly powerful final sections, these complaints come to seem all but irrelevant. If the novel’s first hundred pages are disorienting and occasionally plodding, the last hundred have a rare narrative sweep and force. The broad strokes and bald statements don’t recede, exactly, but they’re like the manipulations of a Puccini opera, so skillful that it seems churlish to object.

And tempering the occasional misstep is the importance of the book’s project, which is to honor and record a nearly forgotten heroism. At the end of the novel, Mateo sees video footage of his mother speaking at a rally, joyous and powerful. “That was the thing about the movement, wasn’t it?” an activist who knew her says. “People came thinking they were dying but they ended up finding out how powerful they really were.”

“Christodora” recounts a crucial chapter in the history of queer life, which is to say in the history of American life. It’s also, for all the despair it documents, a book about hope: In Murphy’s 2021, there is a cure for AIDS.

Garth Greenwell is the author of the novel “What Belongs to You.”

On Sept. 13 at 6:30 p.m., Tim Murphy will be at Kramerbooks at 1517 Connecticut Ave. NW. kramers.com.

Christodora

By Tim Murphy

Grove/Atlantic. 432 pp. $26