Renée Michel is the dumpy, nondescript, 54-year-old concierge of a small and exclusive Paris apartment building. Its handful of tenants include a celebrated restaurant critic, high government officials and members of the old nobility. Every day these residents pass by the loge of Madame Michel and, unless they want something from her, scarcely notice that she is alive. As it happens, Renée Michel prefers it that way. There is far more to her than meets the eye.

Paloma Josse also lives in the building. Acutely intelligent, introspective and philosophical, this 12-year-old views the world as absurd and records her observations about it in her journal. She despises her coddled existence, her older sister Colombe (who is studying at the École normale supérieure), and her well-to-do parents, especially her plant-obsessed mother. After careful consideration of what life is like, Paloma has secretly decided to kill herself on her 13th birthday.

These two characters provide the double narrative of The Elegance of the Hedgehog, and you will -- this is going to sound corny -- fall in love with both. In Europe, where Muriel Barbery's book became a huge bestseller in 2007, it has inspired the kind of affection and enthusiasm American readers bestow on the works of Alexander McCall Smith. Still, this is a very French novel: tender and satirical in its overall tone, yet most absorbing because of its reflections on the nature of beauty and art, the meaning of life and death. Out of context, Madame Michel's pensees may occasionally sound pretentious, just as Paloma might sometimes pass for a Gallic (and female) version of Holden Caulfield. But, for the most part, Barbery makes us believe in these two unbelievable characters.

Unbelievable? Well, let's start with Madame Michel, the very stereotype of the Parisian concierge. Despite her appearance and outward manner, she possesses a mind of the most infinite refinement and precision, loves Mozart (and detective novelist Michael Connelly), regards Purcell's "When I am laid in earth" (from the opera "Dido and Aeneas") as "the most beautiful music for the human voice" in the world, can casually quote from Marx's Theses on Feuerbach ("Whosoever sows desire harvests oppression"), studies and rejects the philosophy of Husserl, shudders at slovenly grammar and even practices the Japanese tea ceremony in her private backroom. In short, this human dishrag, who left school at the age of 12, is more aware and more cultivated than anyone around her. Nonetheless, her inner life is entirely clandestine, and during the day she dons the mask of the dumb peasant that the world thinks she is. But why?

"I was the child of nothing. I had neither beauty nor charm, neither past nor ambition. I had not the slightest savoir-faire or sparkle. There was only one thing I wanted: to be left alone, without too many demands upon my person, so that for a few moments each day I might be allowed to assuage my hunger," a hunger, that is, for books, art, music and speculative thought.

That's what she tells us initially. But there are other, more emotional reasons for Madame Michel's withdrawal into herself, and nearly all of them arise from the great gulf of class. For example, she helped her late husband, Lucien, in overseeing the apartment house, until he grew sick:

"To rich people it must seem that the ordinary little people -- perhaps because their lives are more rarified, deprived of the oxygen of money and savoir-faire -- experience human emotions with less intensity and greater indifference. Since we were concierges, it was a given that death, for us, must be a matter of course, whereas for our privileged neighbors it carried all the weight of injustice and drama. The death of a concierge leaves a slight indentation on everyday life, belongs to a biological certainty that has nothing tragic about it and, for the apartment owners who encountered him every day in the stairs or at the door to our loge, Lucien was a non-entity who was merely returning to a nothingness from which he had never fully emerged, a creature who, because he had lived only half a life, with neither luxury nor artifice, must at the moment of his death have felt no more than half a shudder of revolt. The fact that we might be going through hell like any other human being, or that our hearts might be filling with rage as Lucien's suffering ravaged our lives, or that we might be slowly going to pieces inside, in the torment of fear and horror that death inspires in everyone, did not cross the mind of anyone on these premises."

As you can see, Madame Michel writes in extremely formal prose, though her aesthetic tastes prove surprisingly eclectic. While she is drawn to Japanese simplicity, to those still moments of the turning world when we perceive the beauty within the fugitive and transitory, she's no snob and tells us that anyone who wants to understand the art of storytelling should study the film "The Hunt for Red October": "One wonders why universities persist in teaching narrative principles on the basis of Propp, Greimas or other such punishing curricula, instead of investing in a projection room. Premise, plot, protagonists, adventures, quest, heroes and other stimulants: all you need is Sean Connery in the uniform of a Russian submarine officer and a few well-placed aircraft carriers."

Much of the first part of Barbery's novel simply depicts daily life in the apartment building, as filtered through the sensibility of either Madame Michel or Paloma. The 12-year-old belongs to a long line of sophisticated French whiz kids, and she's able to toss off bon mots with Left Bank aplomb:

"He's so conservative that he won't say hello to divorced people." "As far as I can see, only psychoanalysis can compete with Christians in their love of drawn-out suffering." "A teenager who pretends to be an adult is still a teenager. If you imagine that getting high at a party and sleeping around is going to propel you into a state of full adulthood, that's like thinking that dressing up as an Indian is going to make you an Indian. . . . It's a really weird way of looking at life to want to become an adult by imitating everything that is most catastrophic about adulthood."

But halfway through The Elegance of the Hedgehog, the lives of Paloma and Madame Michel are unexpectedly transformed. A Japanese gentleman named Kakuro Ozu buys a vacant apartment. Though clearly rich, he is also immensely courteous and shrewd, and immediately perceives that neither the little girl nor the concierge is just what she seems. Before long, Monsieur Ozu is gently contriving some little tests to discover more about their secret lives. And this leads to developments that range from the comic to the touching to the heartbreaking.

Madame Michel, in particular, begins to grow confused. Perhaps she does want more from life than books and music and videos. "Human longing! We cannot cease desiring, and this is our glory, and our doom. Desire! It carries us and crucifies us, delivers us every new day to a battlefield where, on the eve, the battle was lost."

Eventually, though, the wavering concierge realizes that she must risk the awful daring of a moment's surrender. Paloma has already prepared us for this leap, when she writes in one of her journal entries about "kairos, a Greek concept that means roughly 'the right moment,' something at which Napoleon apparently excelled. . . . Anyway, kairos is the intuition of the moment, something like that."

Nearly everyone in The Elegance of the Hedgehog takes great care over what the sociologist Erving Goffman once called "the presentation of self in everyday life." And this makes for much of the book's humor. At one point Madame Josse takes Paloma to consult an icily chic Parisian therapist about her little girl's "secretiveness." Eventually, left alone with the doctor, Paloma squares off with him: "Listen carefully, Mr. Permafrost Psychologist, you and I are going to strike a little bargain. You're going to leave me alone and in exchange I won't wreck your little trade in human suffering by spreading nasty rumors about you among the Parisian political and business elite. And believe me -- at least if you say you can tell just how intelligent I am -- I am fully capable of doing this." To Paloma's surprise, her threat actually works.

At one point Madame Michel asks herself, "What is the purpose of intelligence if it is not to serve others?" What indeed? Certainly, the intelligent Muriel Barbery has served readers well by giving us the gently satirical, exceptionally winning and inevitably bittersweet Elegance of the Hedgehog.