Such reactions came not only from casual observers confused by his boorish manners and dismayed that he didn't draw "straight". It was Cezanne that Emile Zola, his old school friend from Aix-en-Provence, had largely in mind when he wrote a novel about an artist doomed to failure by "heroic madness" and defective vision. In fact the cues for this could have come from Cezanne himself. "I am a primitive, I have a lazy eye," he would protest in his later years. He was afflicted by "brain trouble" and was "no longer my own master".

Danchev's new life - original, engaging and highly persuasive - brushes aside that line in pathos, likewise refusing the "profitless psychoanalysis" that many a distinguished interpreter has applied to the artist. The problems of Cezanne, Danchev argues, were of his own conscious choosing. The ambitious and well read young Provencal, coming to Paris just as a new art scene was coalescing around Edouard Manet, began pretty early to stake out his own independent path.

"In the mid-1860s, at the age of about 25, Cezanne set about becoming Cezanne." Socially, that involved developing a sardonic, forbidding crust, posing as a querulous hick from the sticks. (On being introduced to the dapper maestro of modern painting: "I won't offer you my hand, Monsieur Manet, I haven't washed for a week.")

Intellectually, it meant taking seriously France's leading philosopher of the day, Hippolyte Taine, who wrote that real art came about through "sensation" driving the brain "to rethink and transform the object, sometimes to illuminate and elevate, sometimes to twist and distort". What was this "sensation"? Perhaps it meant the impulses of lust and violence Cezanne's early paintings often featured; perhaps it was the rhythmic intuition about two-dimensional relationships that literally distorts the dinner plates and the Monts Sainte-Victoire in his later work. "I have very strong sensations," Cezanne would remark.

In Danchev's account, that becomes a boast that the painter requires himself to live up to, a persona to inhabit: "Performing Cezanne became one of his best turns."

The tale is largely of how the role expanded and deepened, spurring him on to prod at strange new fault lines in the field of vision and, in the decade before his death in 1906, to act as guru to a select few listeners who come to seek him out in his Provencal lair. Also, of how he "immatured with age", as Danchev puts it, letting his self-appointed wildness take over the reins. We hear of a neighbour covertly watching him as he puzzled over a Mont-Sainte-Victoire: "He seemed to be all out of sorts … Do you know what he did? He picked up a big rock and threw it right through the middle of the canvas!"

The tale largely turns on these considerations because, outwardly, it is far from incident-packed. Cezanne pursuing his 19th-century research project more resembles a gentleman scientist such as Charles Darwin than struggling peers such as Claude Monet, in that his father, a banker, ensured he never depended on sales.

Louis Cezanne, it is true, halved the allowance when he found out that in Paris, the nearly 40-year-old Paul had long been keeping a common-law wife and their child. But Marie-Hortense Fiquet is almost the only amatory interest in the artist's career, and although Danchev valiantly tries to see her in three dimensions, the evidence is just too slight to gain purchase - especially as she never looks the same from one depiction by her husband to the next. (As Danchev nicely puts it: "A Cezanne portrait is more a thereness than a likeness.")

During Cezanne's financial contretemps with his father, it was Zola, the schoolfellow turned literary celeb, who stepped in with loans. It's long been assumed this friendship of Cezanne's was betrayed and broken when Zola published his melodrama about an artist doomed by "heroic madness". But again Danchev reads the evidence more subtly. He portrays a more gradual divergence, ending with in one corner a political loudmouth, hosting suppers in his mansion outside Paris, while in the other a no less proud recluse shunts canvases in and out of a self-designed studio on the outskirts of Aix.

With relatively little to work with dramatically, Danchev creates his Cezanne by a method that in less capable hands would seem outrageous. He assembles him out of emotions gathered from other people's lives. How did Cezanne feel about his father? Let's read what Franz Kafka had to say about his own. For Cezanne's sense of self-worth, go to Paul Valery writing about Stendhal. A Samuel Beckett short story gives us an angle on the eventual marriage to Marie-Hortense; while Gustave Flaubert can voice whatever disdain the artist felt for critics, the bourgeois and his fellow Provencals.

Equally, the paintings come to life as they have lived in others' eyes. Ginsberg's poetic witness is joined by Seamus Heaney, Derek Walcott and Rainer-Maria Rilke, whose letters about a 1907 Cezanne retrospective remain more vivid than anything written about the paintings since. Stan Brakhage, Alberto Giacometti and Martin Heidegger all put in a word. Danchev seems to report back from a cultural meta-space in which high artistic achievements in every medium and from every era interconnect.

Why should we trust him to do so? First, because his own prose is so witty, mobile and sensitive; second, because to a lay reader it seems grounded in long and thoughtful study of the primary sources; third, because that study brings out how committed a reader Cezanne himself was, a devotee of poetry from Virgil to Charles Baudelaire. This feeds Danchev's argument that the imagination of this alleged obsessive was "richer than is generally realised, and rather less strange". Danchev paces around the chronology fairly freely, pursuing whatever line of thought engages him, genially holding the stage.

Trying to close in on Cezanne's landscapes and still lifes from the years before his death at 67, the approach does hit a limit. In the face of those uniquely momentous arguments between eyesight and the world, one instinct tells Danchev to pile up appreciations and circumstantial data and another, more wisely, to submit to silence. Seeing beyond the outward man, the supposed fractured sociopath, he would like to relay the substance of the painter who undertook to deliver "truth" in his art: "Cezanne's truth may be more important than Cezanne's doubt."

But that truth is for showing, not telling. These pages reach their high point with a photo of an old man in a hat and tatty jacket, standing between a country wall and a tripod easel, brush poised before the canvas, eyes staring out. Transfixed, Danchev's happy eloquence for once stutters to a stop. "He is painting. This is it."