In the world according to John Irving, sex is serious business. Subjects like sexual violence ("The World According to Garp") and abortion ("The Cider House Rules") have been central to his work, and now in his pensive 13th novel, "In One Person," he tackles an equally urgent question: American society's slow, painful effort to comprehend issues of sexuality and gender identity.

Like other Irving novels, much of this one is rooted in a decidedly downmarket New England prep school -- Favorite River Academy in the town of First Sister, Vt. Billy Abbott, a novelist and the story's first-person narrator, examines his life in old age, describing the roiling tides of bisexuality he discovered as a student at the all-male school. Traveling from Vermont to Vienna and spanning a period from the mid-1950s to the present, Billy's story probes complex, divisive issues of gender identity with sensitivity and humanity. It's a period in which society's attitude toward homosexuality slowly evolves, one tragically marked by the AIDS epidemic, a nightmare episode depicted in often harrowing detail.

This is Irving's most political novel since "The Cider House Rules," but an air of sadness, not anger or passion, permeates it. It seems he wants to lower the volume of our raucous public conversation on issues such as gay marriage by constructing the story around a group of customarily odd, but intensely appealing, characters. Whether it's Billy's cross-dressing, sawmill-owning grandfather, First Sister's librarian who harbors her own sexual secret or a host of others (straight, gay or bisexual) who struggle to find love and meaning in sometimes unconventional ways, they're never mere surrogates enlisted in the service of Irving's social agenda.

Irving's fans will feel the warm glow of recognition at encountering familiar tropes: a writer-protagonist, wrestling and even bears (in a fashion). But, at times, some of those devices -- his resort to recurring phrases or character tics (the wrestler obsessed with his weight who's constantly "rinsing and spitting") -- can grow tiresome. Even with a fatal car accident and a messy suicide, there is less of the random violence that has marked Irving's fiction, and few hints of his darkly comic sensibility. Perhaps that's why the novel lacks the manic energy of predecessors like "Garp" or "The Hotel New Hampshire" and occasionally meanders.

Despite its compassion and generosity of spirit, "In One Person" probably isn't the best gateway into John Irving's body of work. For that, the clear choices are "Garp," "Cider House" or "A Prayer for Owen Meany." Still, it's an admirable undertaking, evoking the spirit of his literary hero, Charles Dickens, to examine a serious social issue without losing sight of the truth that those ultimate questions are rooted in the everyday world of living, breathing people.

Harvey Freedenberg is a freelance reviewer and member of the National Book Critics Circle. He writes from Harrisburg, Penn.