Ask almost any pianist - one could almost say any musician - who was the greatest of the 20th century, and the chances are that you will be told Sviatoslav Richter. Music is not a competition; there are few more pointless pursuits than the musical equivalent of deciding whether Jack Hobbs or Don Bradman was truly the greatest. Schnabel, Gould, Fischer, Michelangeli - to single out, quite arbitrarily, just four - were all unique geniuses. But none had the combination of range, depth, technique, sound, command and sheer musicianship of Richter. To hear Richter play was to be transported from this world into another universe, where nothing else mattered but the sound coming from the piano. (Not least because he insisted, in his final years, on playing in near total darkness, with the single, small stage lamp that illuminated his score having the effect of both drawing you in, to focus on the piano, and closing off any possibility of watching the man rather than listening to the music.)

I was lucky enough to hear Richter play on a number of occasions. The composers he chose were typically varied: Bach, Beethoven, Shostakovich, Chopin, Mozart, Haydn, Schumann, Prokofiev and Hindemith. But for me, it was his Schubert, above all else, that was truly miraculous. I can still remember the effect of his G major Sonata, a decade after the concert.

Recordings never do justice to the real thing. But, for all Richter's ambivalence to the idea of capturing for eternity a moment that, by definition, should be spontaneous, he left a large legacy, many worthy of his memory. His Well-Tempered Clavier (Bach), his Pictures at an Exhibition (Mussorgsky), his Liszt Sonata and the recent BBC archive releases of his Schubert provide a wonderful illustration of the sheer variety of his mastery.

But for a rounded indication of Richter's genius, Bruno Monsaingeon's edition of his notebooks and edited conversations is indispensable - as well as being pure joy from start to finish. Monsaingeon has taken his conversations with Richter, which were recorded in his compelling documentary, Richter: the enigma, and has edited them into a narrative. Wisely, it does not attempt to be comprehensive or chronological, but rather aims to give a flavour of Richter's often wilful personality. He was full of paradoxes. He hated arranging anything, whether it was a concert or a journey, and he hated travelling as part of a schedule. But he was utterly rigid in his practice method: constant repetition of the same phrase, then the next, then the next.

He was, in effect, trapped behind the Iron Curtain until 1960, yet felt no pressing urge to see outside. Indeed, as he puts it: "How many times afterwards have I thought of how happy I'd have been if only I'd missed the train. I'd never have got to know America, and would have been all the better for it . . . The noise, the cheap culture, the advertising and the language!"

But when left to his own devices - no promoters, no advance bookings, no scheduled programmes - he loved to travel. He was at his most relaxed when he simply got behind the wheel of a car, stopped wherever he fancied and gave an impromptu concert. When he was well over 70, he drove from Moscow to Japan and back again, giving nearly 100 such concerts in a few months while crossing the Urals and Siberia.

Monsaingeon includes selections from the notebooks into which Richter poured his thoughts, whether it was after performing or listening. These 200 pages alone make this a book to savour. Thus is Vladimir Horowitz despatched in one paragraph: "Phenomenal and off-putting and excellent and fantastic tone, and thoroughly contradictory. Such talent! And such a trivial mind . . . Such a sympathetic person, so artistic and yet so limited. It's all so strange."

The great conductor Kurt Sanderling said of Richter that "not only can he play well, he can also read music". That just about says it all.