Geordie Greig's biography of Lucian Freud: 'A stitching together of racy tabloid features'

An intimate and unpretty memoir of a private person – which the late artist would have loathed

During his lifetime, the painter Lucian Freud guarded his privacy. He chose to see whom he saw, and did so entirely on his terms. He kept friends, lovers, acquaintances separate from one another. He seldom gave out his telephone number. At any private view of his work, you could be sure of at least one thing alone: Freud himself would be absent.

He was not to know that at a certain point in his later life a charming young Etonian called Geordie Greig, currently the editor of the Mail on Sunday, would take it upon himself to get to know the great no-show. The project was hatched after Greig found himself visually ravished by an exhibition of Freud's paintings at the Anthony d'Offay Gallery when the author of this memoir was still a schoolboy. In time, thanks to Greig's tireless stalking of his victim, that encounter would develop into a fully blown friendship of trust.

In fact, during the last decade of Freud's life, as this book documents so meticulously, Greig became a favoured friend at the breakfast table. Not long after the book begins, we see photographs of Freud with Greig's young children at Sally Clarke's restaurant in Kensington, where those breakfasts took place. We even read a note in Freud's childish hand referring to one of those breakfast meetings: a talismanic detail, we are perhaps supposed to think, heart-flutteringly.

Earlier still, cunning Greig had inveigled Freud into being photographed by a very clever ruse indeed. He told him that he wanted to take a photograph of Freud's oldest friend, the painter Frank Auerbach, a fellow exile from Nazi Germany, and asked Freud whether he would be in the frame too. Freud, who loathed the random attention of photographers, agreed – for Auerbach's sake. Greig quietly boasts that, at the point he gained Freud's assent, Auerbach had not even been approached.

In short, this is the kind of intimate and unpretty memoir that Freud would have utterly loathed, and which its prurient readers will delight to read. It unzips Freud. It describes his single-minded dedication to painting and shagging and outrageous gambling – the three uproariously risk-taking pursuits went hand in hand. Freud's selfishness, his disregard for the feelings of other people, seem almost saintly in the purity of their single-mindedness. He went after what he wanted, and he generally got it. His was a life lived extravagantly on the outer edge.

Alas, the book is not quite what Tom Wolfe, trumpeting its virtues on its jacket, tells us to expect. It is not a flawlessly crafted portrait. It tells us a lot about the mess and the mayhem and the horror of Freud's life, but it is not written especially well. And in spite of the fact that it may look rather glamorous, it is quite sloppily edited too – how can any self-respecting publisher overlook the fact that Damien Hirst's surname is not spelled Hurst? In fact, it reads like a stitching together of a collection of racy tabloid features.

Unsurprisingly, the book has been crawled over by lawyers, such is its defamatory potential. Entire chorus lines of life models-turned-lovers high-kick through its pages. Yet some are treated with kid gloves. Kate Moss gets very careful treatment indeed. There is no suggestion that he bedded her. The book's rawest moments concern his umpteen hard-done-by children (certifiably 14, but perhaps more still waiting to declare themselves): how they admired and felt betrayed by him in just about equal measure for his indifference, his coldness, his absenteeism.

The story ends well for Freud himself. Having spent so much of his life living in the shadow of Francis Bacon, that international art celebrity, Freud's reputation – and his prices – soared in the last 15 years of his life. A New York dealer by the name of William Acquavella took him on, his eighth. He alone did what Freud always demanded from his dealers. He paid him in cash, up front. By his death, Freud's undying commitment to figurative painting no longer seemed yawn-worthy.

Breakfast with Lucian: A Portrait of the Artist is out now.