Late in John Irving’s 13th novel, “In One Person,” the narrator, an aging writer named William Abbott, recalls visiting a high school friend who was dying of AIDS. It’s the early 1980s, the beginning of the AIDS crisis, and Irving evokes the deathly terrors of that period, a time when people seemed, literally, to evaporate, to become in the words of the late David Wojnarowicz, “a dark smudge in the air that dissipates without notice … glass human(s) disappearing in rain.”

As Abbott shares with his friend’s 15-year-old son the story of a summer trip to Europe, the boy’s mother interrupts from the other room: “Peter! … Come here — let your father rest!” It’s an arresting moment, not least for what the friend is asking: that Abbott look out for his child after he and his wife (whom he’s infected) are gone.

Abbott and the dying man had a fling during that long-ago European summer, which brings an undertone of complicity, and recrimination, to the scene. And yet there’s something else at work, some sense that the moment isn’t quite authentic, that the situation, if not necessarily the emotions, have been staged. It’s all in the timing, the way Abbott is barely allowed to get started: “It was entirely orchestrated — the whole thing was rehearsed. You know that, don’t you, Billy?” asks another friend, Elaine, who has accompanied him.

As for why this resonates, I want to posit that it tells us something about “In One Person” — not the plot of the novel so much as the mechanics of the plot, the construction of a narrative that itself seems orchestrated and rehearsed. This may not be Irving’s intention, but the deeper we get into the novel, the less we believe it, seeing the people here as not quite three-dimensional, manques for the larger issues the book means to address.

In brief: Abbott is bisexual with an attraction to men, women and transsexuals. Growing up in the 1950s in the town of First Sister, Vt., he is surrounded by a surprisingly gender-fluid cast of characters, from his Grandpa Harry, a cross-dresser who plays female characters in the local theater, to Miss Frost, the mannish town librarian whose reserved demeanor masks the open secret of her past.

This being a John Irving novel, there is the usual medley of wrestling, family dysfunction and single parenthood; there are scenes set in Vienna, and much of the book, like “The World According to Garp” before it, takes place at a New England boarding school. At times, the whole thing feels like a mash-up, drawing elements from “Garp,” “The Hotel New Hampshire” and “A Widow for One Year,” although it doesn’t reframe those novels so much as it refracts them, tracing an unlikely line through territory we’ve seen before.

That is — or should be — a good thing, a writer revisiting his material from a different angle, turning (or re-turning) it over and over, seeing it through a fresh lens. But “In One Person” never delivers on that sense of freshness, settling for a posture of contrivance instead.

This starts with First Sister, a town, like many in Irving’s fiction, where eccentrics are tolerated, embraced even, and the values of community outweigh those of the status quo. It’s a nice sentiment, if unrealistic, and it casts the entire novel in a sentimental glow.

“In One Person” may be a book about AIDS, about sexual identity and the loss that accompanies growing up, but its overriding tone of acceptance means that the struggles of its characters, especially Abbott, never seem particularly fraught. “Billy, Billy — you’ve done nothing wrong!” a boarding school teacher tells him when he confesses that he has crushes on men and women, an enlightened perspective for 1950s New England and one that smooths out the complexities of the situation, leaving little but a kind of social correctness behind.

Don’t get me wrong: I agree with Irving here, as I do with pretty much everything he has to say about sexuality. I’m respectful of the guts it takes for a mainstream novelist to embrace sexual politics in this culture, even as it saddens me that this is still the case.

That’s a key problem with “In One Person,” that it makes sexuality seem too easy, when everything we know about the society in which we live tells us that it remains otherwise.

Nowhere is this more troublesome than when it comes to Jacques Kittredge, a prep school golden boy who is in his way the id to Abbott’s ego, although their relationship is never fully clear. Wrestler, actor, teenage Lothario, he occupies the emotional center of the novel, the object of crushes by Abbott and his friend Elaine (whose mother is the teacher to whom Abbott confesses). If Kittredge rebuffs them both at first, he later grows to share “their sad envy, (their) familiar and pathetic longing.”

Theater is the tool of this realignment; indeed, the very notion of drama, with its role reversals, its costumes and performance, becomes a metaphor for the shifting realities of the world. Irving highlights that by casting Kittredge, Abbott and Elaine in a series of Shakespeare plays, using the similarities — “Don’t you see, Bill?” Grandpa Harry explains. “Viola is a cross-dresser. That’s what got Shakespeare in trouble!” — to reflect on his text.

And yet, here as well, things happen too easily, without the necessary friction to make us care. After Abbott’s first sexual experience ends in embarrassed exposure, it is Kittredge who embraces him. “Way to go, Nymph!” he declares. “I am so impressed with you — you are my new hero!” Abbott is skeptical; “I knew enough to be careful,” he tells us. “With Kittredge, you were never sure where the conversation was headed.”

Still, there is no fallout, no moment when the narrative turns. Later, we discover the reason for this: Kittredge too is sexually conflicted … or not quite conflicted (there is hardly enough conflict in this novel). It’s a nice idea, yet like so much, it seems to come out of nowhere, to have more to do with the point Irving wants to make than the story he is trying to tell.

In the end, this is where “In One Person” stumbles, when it tries to fuse social commentary with art. That isn’t to say one can’t write a political novel, but the politics have to emerge from the characters, not the other way around.

There’s much to admire about Irving’s willingness to stake out a position here, as he has — “Garp” is, among other things, a novel about women’s rights, while “The Cider House Rules,” his greatest book, revolves around an abortion provider — throughout his career. Yet I wish he’d paid closer attention to the tensions, to the complications, of growing up as a sexual outsider in a culture where the desires and the pleasures of the body are still anathema.