Nicholson Baker has been recognized by-ahem-discerning readers as a brilliantly original writer since his first novel, “The Mezzanine,” appeared in 1989. (The plot: a man buys shoelaces. Baker made it work.) But his last book,“U&I,” a jaw-droppingly frank (and knee-slappingly funny) essay about his fixation on John Updike, left no doubt that Baker wanted to be flat-out famous. His new novel, “Vox, " ought to do the trick. It’s not only about sex-a subject that never lowered a writer’s profile yet-but it homes in on the Zeitgeist like a Patriot on a Scud, or was it a Scud on a Patriot? Already, weeks before official publication on Valentine’s Day, Baker has been profiled in Vanity Fair and Mirabella; last week The Washington Post’s Style section splashed his face on the front page, literally big as life.

The plot: Jim and Abby (no last names, please) swap fantasies over a telephone “party” line, have orgasms and hang up. These strangers instantly tell each other their gamiest secrets, and become evasive only about such superficial details as what cities they live in. Obvious irony, you say? Go to the bottom of the class. For Baker, irony is old hat; his method is a microscopic, distortion-free clarity-a sort of literary fiber optics-that makes conventional figure-me-out modernism seem stupidly coy. Is “Vox” really a post-AIDS tragedy of nonconnection, or is it really a techno-safe-sex love story? Correct answer: yes, it really is.

Another possibility: is “Vox” just a stroke book for smart people? Well, not just. But it’s safe to say Baker wouldn’t kick if it got you aroused: of the possible readings of “Vox,” among the least likely is that it’s a warning against the evils of self-abuse. Jim is shy about telling Abby he saw the ad for the phone service in a magazine called “Juggs,” but in fact he’s perfectly safe with her. They both like to pleasure themselves: that’s what brought them together, if this is together. So how hot is “Vox”? Not bad, if you don’t mind a shortage of the old in-and-out; very, if you share Jim’s tastes. “I think it’s fair to say that you are interested in women masturbating,” says Abby, after he’s gone on about it for pages. “Any woman masturbates anywhere,” he agrees, “I want to know about it.”

“Vox” isn’t just Baker’s hottest book; it’s also his warmest. We know little about Jim and Abby beyond how they talk and what gets them wild; still we genuinely get to like them. But despite the reputation it’s bound to get as a shockeroo, “Vox” is nowhere near as risky-or even as intimate-as “U&I.” Liking this or that way of working up to orgasm isn’t such a big deal-everybody likes something-but literary ambition is truly a shameful pleasure.