In One Person, By John Irving

Irving's versatile writer-hero wrestles with inner demons and social stress in a sexual comedy that has both guts and heart.

American fiction dotes on its plucky rebel kids – those clear-eyed but big-hearted outsiders and vagabonds who from Twain to Salinger, and far beyond, light out for the territory of a hard-won liberty. No one, over three decades, has worked this seam with more zest and glee than John Irving.

His eccentric and beloved potboilers, from The World According to Garp on, bring off one acrobatic feat of high-wire virtuosity after another. Somehow, Irving can make the overblown family melodrama and the cornily theatrical intrigue fly. Meanwhile, his quirkily compassionate individualism reliably stands up for the upstart and the outcast.

Erotic choices, and sexual destinies, have repeatedly acted as his touchstones. Irving commonly wages war on the bigot, the prude and the bully, but seldom with such effusive brio as in his 13th novel. In One Person follows its bisexual hero (a writer, as so often in Irving) from the shame and confusion of the uptight late-1950s through the era of gay liberation – which brings with it new bars of every kind – to the Aids epidemic, the proud resistance to its onslaught, and the uneasy tolerance of today.

In one of Irving's wackily self-sufficient New England private schools, set in a logging town thronged with colourful oddballs, young Billy Abbott falls for cool, commanding Miss Frost. As the gender-switching town librarian of First Sister (and who knew that the forests of Vermont harboured so many transsexuals?) insists, "My dear boy, please don't put a label on me – don't make me a category before you get to know me." Billy, and Irving, love this shape-shifter's slogan so much that it recurs at the finale.

Billy's fugitive father, a precocious wartime code-breaker, has fled wife, child and state for a same-sex future that we predict long before son meets aged dad-in-drag on stage in a Madrid bar. Back at First Sister Academy, Mom remarries. The good stepfather Richard Abbott – theatre buff and moral lodestar – guides his young charge's erratic path towards maturity. Irving plunges with gusto into the squalls and scandals of life in a rough-hewn neck of the woods stacked with Kant's "crooked timber of humanity".

For two-thirds of the novel, we wolf down In One Person as a bewitchingly offbeat school story set at a transvestite Greyfriars or a pansexual Hogwarts. Irving's closed-world comedy has a Wodehousian lilt at times. Sawmill-owner and twinkly sage Grandpa Harry perpetually dons frocks and gowns for Richard's stage productions. It all rather resembles the Monty Python lumberjack song come to life.

Blow by blow, shock by shock, Billy escapes his "self-contempt". He discovers his vocation as an author (his mother has said that "novels are just another kind of cross-dressing") and, equally, as a lover of both men and women – not forgetting glamorously in-between Donna. But Billy and Elaine – his life-partner more than his bed-partner – will brood forever over the cruelly seductive First Sister athlete Jacques Kittredge. This homme fatal pursues a fate that mirrors the novel's gender-crossing motifs. And, this being an Irving plot, charismatic Jacques must be a champion wrestler too – as indeed was Miss Frost, when she answered to the name of "Al".

In One Person loses some of its tenderly farcical grip when grown-up Billy makes his way through bohemian Manhattan. Soon Aids tags along to shadow every step, and "my friends and lovers kept dying" . A few scenes do showcase Irving's truly Dickensian generosity of imagination. The slow death at home of Billy's former schoolmate, with wife and son in loving, bewildered attendance, reveals a master's hand. Yet Billy, and his readers, miss the rambling idiosyncrasies of First Sister. At 70, he returns there to teach, to mentor sexually questing youngsters and – in a stagey climax – to wrestle repentance out of a thuggish jock.

In summary, Billy Abbott's circular progress sounds like a manifesto built on paradox. Irving hammers home the values of plurality. Dogmatically, he defends diversity. Single-mindedly, he recommends self-doubt. Yet the freewheeling comedy neutralises any drift into preachiness. Loose-limbed but then suddenly tight-wound, this is a hard novel to classify but an easy one to like – much like its protagonists. In the enchanted woods of Vermont, Rilke's angels and Shakespeare's sprites cast spells that conjure dreams of a love without limits.