Yellow shoes are the only giveaway. Without them, Steve Martin's just another New Yorker in a somber gray coat, braced against the coming winter, out Christmas shopping for his wife; just another writer with a new book he will see in the window of Rizzoli, or Barnes & Noble on Fifth Avenue.

"An Object of Beauty" is Martin's third novel — the first two are "Shopgirl" and "The Pleasure of My Company," both set in L.A. — and he seems confident that it will be well received. He admits that he felt much more "sure-footed' with this book and it was his least edited, but he's also grateful for the advice of friends who read the work and surprised by how much a good suggestion can improve a piece of writing.

" Carl Reiner once gave me some good advice — 'tell 'em the rules in the first two minutes.' That's what I try to do in my books, establish the rules, set the tone in the first graph. An art dealer, a friend, once told me that all you have to do is put the painting in front of a collector and stand back. That's what I try to do," Martin says.

The art world of the new novel is one that Martin, who has been collecting since the 1970s, knows well; some of his closest friends are dealers and gallery owners. Most of the action takes place on four blocks between 74th and 79th streets on Madison, Sotheby's on 72nd Street and York Avenue, and a gallery or two below 26th. It stars Lacey, a charismatic animal in her 20s who enters the New York art world in the 1990s through the front door (at Sotheby's) and leaves it through the back (home in Atlanta).

Unlike Mirabelle, the wan, depressed heroine of Martin's novel "Shopgirl," Lacey is on her way up, "though her path," we are warned, "often left blood in the water." Martin created these two very different young working women, canaries in the coal mine, not for political/gender reasons but because they both give him a chance to say something about the larger culture — Lacey gets ahead by damaging those around her; Mirabelle is wounded by the world. Mirabelle finds some refuge in love. Lacey does not.

We are having lunch at Trattoria dell'Arte, steps from Carnegie Hall, on one of those crisp blue, cold days when New York looks fairly clean and very expensive. Martin has the table in the back, but anonymity eludes him — he shifts, annoyed, when a diner at a nearby table starts to videotape him on a cellphone. He positions himself so that he is hidden from view by his interviewer.

Like "Shopgirl," which began with the image of a girl selling gloves (at Bergdorf's, though it became Neiman Marcus in the novel) this new book began with a small scene, carried in the author's imagination for several years before entering the world as a novel. In "An Object of Beauty," the image was of a Frederic Remington print. Martin imagined its owner, desperate for money, finding that the print was actually a painting.

This happens to Lacey, whose education in art appreciation, Martin admits, mirrors his own. Through the novel, she learns not only how to appraise the financial worth of a painting, but what it means to want a painting and what it means to live with a painting.

"When I was younger," Martin explains, "I thought, am I supposed to have a profound experience looking at a painting? With music, even with books, that comes more naturally. The first painting I ever owned was a simple, antique-store find; a lighthouse, moonlight on the water, that sort of thing. I found that it wasn't until I spent time alone with it that I had any kind of communion with it."

Martin's specialty is American art, mostly 20th century — in 2005 he donated $1 million to the Huntington Library, Art Collections and Botanical Gardens for the American Art division. He wanted to show Lacey's true art education at Sotheby's — from her first auction, a Tissot, through Vermeer and then the Americans: John Singer Sargent, John Frederick Peto, Milton Avery, Willem de Kooning, Andy Warhol, to name just a few of the artists Martin includes in her (and his readers') education.

In the novel (and in various interviews), Martin says that collecting is like shopping. But it seems that there must be more to it. One of the first paintings Martin purchased was a Ruscha, which he later sold. When asked about the Hopper he sold in 2006 for $26.8 million, Martin shrugs — he hadn't allowed himself to get too attached to that Hopper — he kept the one he really cared about. He describes the feeling you get when you see a painting you want to own: at first, he says, "there's a feeling of giving up, of defeat. That's when you know you have to have it, even if it's unattainable."

Though the novel is set almost entirely within the art world, there is a funny scene on a train when Lacey has a conversation with a writer who theorizes that great paintings gravitate to big money for Darwinian reasons — if they weren't highly coveted, they might end up "in basements and garbage heaps." "Tell me your name again," Lacey asks the writer. " John Updike," he says.

After a questionable episode at Sotheby's, Lacey is quietly fired. She goes to work for a dealer named Barton Talley, an experienced dealer who long ago made the decision about what kind of person/art dealer he wanted to be (the kind with real integrity). Martin says that if the novel ever became a movie, this is the character he would be most likely to play.

The novel is told to us by Lacey's old friend Daniel, a young art critic who slept with her once back in college and who remains fascinated (though not in love) — as one might be with an object, say, a beautiful painting.

"I decided after a year or so of working on the book that a reader really wouldn't want to be in Lacey's head," he said. "I didn't want to have to explain what was in her head — the way you wouldn't want to have to explain a painting. I needed someone to watch, to observe her. After all, paintings don't speak; it's almost impossible to get inside an artist's head. And paintings are not verbal, which is why I wanted to include the color photos of the paintings."

Martin says he chose the 1990s because it was a period of fractured identity — one that began in the 1980s — in the New York art world, a post-minimalism lack of isms.

Martin is remarkably even-handed in his depiction of the art world, describing its leaps and plunges, how taste and culture and money affect it, as if he were writing about physics: "Just as gravity distorts space, an important collector distorts aesthetics. The difference is that gravity distorts space eternally, and a collector distorts space for only a few years."

It's clear that of all the projects he has going at any given time, the writing gives him a feeling of freedom. He is grateful that he doesn't have to write for money, but perplexed by people he meets who say they have something they want to write, but don't want to take the leap without knowing that it will be published. "It seems to me that they should just go ahead and do it," he says, "without thinking about who will buy it, or whether anyone will read it."

Salter Reynolds is a writer in Los Angeles.