WHAT do we know or think we know about great ballet dancers? That they suffer for their art, that they live in fear of injury, that their careers are brutally short. It was the Royal Ballet's Anthony Dowell who ruefully observed that no sooner has a dancer learnt how to do the job than it's time to call it a day. Yet the subjects of this picture-biography - Ekaterina Maximova and Vladimir Vasiliev, stars of the Bolshoi and widely acknowledged as one of the greatest ballet partnerships of all time - have apparently managed to extend their stage-life well beyond the usual limits. He, conventionally enough, has neatly dovetailed dancing with choreography and this year, at 55, was appointed Artistic Director of the Bolshoi. But she ...?

Those who saw Maximova in 1989 guesting with English National Ballet will testify to the phenomenal qualities of a 50-year-old who could and did inhabit the skin of a young girl. Even so it is hard to believe that seven years on Maximova is continuing in this vein. A detailed list of the dancers' entire repertoires at the back of the book reveals that in 1994 Maximova created, in a new ballet at the Bolshoi, a role simply called "girl". The author does not address our incredulity.

Other personal issues are skated over too. If only by omission, the author lets us assume that Maximova is content still to be living in her mother's house in Moscow, despite being married to Vasiliev for 35 years and having had the world at her feet. How did she and Vasiliev feel about the dancers who defected - including Irek Mukhamedov, not so very long ago their colleague at the Bolshoi? What of the sacrifices they have made: private life, family life?

Frustratingly, Roberta Lazzarini did not conceive this handsome picture book as a biography, even though it follows a rough chronology. It is more a eulogy to the dancer's art, drawing chiefly on the artists' reflections on roles they have made their own over a period of more than 30 years. Giselle and Albrecht, Romeo and Juliet, Tatiana and Onegin, Phrygia and Spartacus, Aeola and Icarus, Masha and the Nutcracker Prince. Lazzarini first saw the pair dance during the Bolshoi season at Covent Garden in 1963 and has followed them ever since - at home in Moscow and on tour around the world. Both are famously shy of self-promotion and this is the first book to be written about them. It reads as if the subjects they were prepared to discuss were strictly prescribed. Our art, not us.

The story Lazzarini wants to tell is in the new photographs - 160 of them, selected from the author's collection of more than 5,000, which in itself suggests something of an obsession on her part. All are black and white, and we would not wish it otherwise. They are glorious.

Many have the gauzy chiaroscuro we associate with film stills from the 1920s. Nevertheless, most present-day photographers with sophisticated equipment would kill to take pictures like these. Very few are posed. Many are taken literally in flight. Some reveal the tedium, the pain, and also the humour, of preparation in the studio. All of them confirm what we read, that those two were not just great dancers, but sublime, unsurpassable. She, in a single moment, embodies extremes of fragility and toughness. He radiates greatness of spirit. This is a book not just for the balletomane, but for anyone intrigued to know quite how high this heavily coded theatre art can aspire.