When Michael Peppiatt visited Balthus at his Italian home, they climbed together "the sharp flight of steps that served as the villa's belvedere". There, gazing down at Rome, the artist remarked: "When one sees what happens to one's paintings, the question becomes: why go on painting?" In this enthralling book, Peppiatt addresses this question in different ways but never insists on an answer.

The art of the critic-interviewer is, like that of the psychoanalyst, to draw poignant attention to what it is that the interviewee cannot express. The limitations imposed on Peppiatt are those of language itself, and they serve him well, causing him to nudge each of his subjects to the point where words fail them, to where the picture, the sculpture, the building or the photograph becomes the only means of expression.

These 28 interviews and 13 studio tours illuminate many abstractions, and many particulars  of workspace, childhood and technique. We visit the "Aladdin's cave" in which Peter Blake painted, the "bookish" haven of Henri Cartier-Bresson, the "supernatural neatness" of architect Richard Meier. Each emphasises for Peppiatt a facet of the artist's work, as if the surroundings were a visible extension of personality.

In the service of his large-scale composition, none of Peppiatt's lines of inquiry  material, cultural, gossipy, psychoanalytic  is allowed to predominate. Instead, each interview refracts the multiple concerns of artists and critic. "I'm just a salad of comings and goings," says Miguel Condé. "Chance and accident are the most fertile things at any artist's disposal," says Francis Bacon.

When required, Peppiatt's grounded intelligence tugs his interviewee's most nebulous thoughts back to earth. Talking about paint, he asks Hughie O'Donoghue: "Is it a voluptuous thing?", to which the artist replies: "Absolutely."

When Peppiatt does sanction a flight, it is always an endearing flight of fancy. Dado tells him: "When I've done a drawing, the person I've brought to life will then walk past the window." "So it's life imitating art," says a giddy Peppiatt.

We come to know the critic through the wit, the characteristic forward dash of his questions. Examining with Auerbach the painter's friendship with Bacon and Freud, Peppiatt wonders politely if "the rivalry came through admiration"? And he cuts a consistently lovable fanatic, ready to wade through "waist-high waters in Venice to talk to Ida Barbarigo" or to be slapped so hard on the back by a jovial Hans Hartung that he "fell to the floor". He is equally unfazed by Zoran Muic's silences or the fact that "Condé speaks almost too well". Gradually we arrive at an impression both of the psychic riot of each artist and, along with it, of that unifying critical sensibility which led Peppiatt to define "the London School" of painters in the late 80s.

If the book risks anything so confining as a perspective, it is one of existential robustness. On that belvedere above Rome, in the presence of Balthus's majestic despair, Peppiatt notes, in contrast, the sudden "thunderous arrival of Balthus's two dogs, still possessed by some adventure in the garden's undergrowth". After RB Kitaj explains: "I even revise the intentions I had when I did [the paintings]," Peppiatt agrees that this "can be a bit alarming", which leads Kitaj to quote from the Kabbalah: "The book changes its meaning every year,'' he says. "Everything is in flux."