For The St. Petersburg Times Rudolf Nureyev (l) and his family pictured in the late 1950s when the dancer began his career with the Kirov (now Mariinsky) Ballet. Nureyev’s last performance was in 1992.

Brilliant, thorough, clear-eyed yet also profoundly affectionate, “Nureyev: The Life,” by Julie Kavanagh — author of “Secret Muses,” a biography of the choreographer Frederick Ashton — is so unusual in its depth of both reporting and integrity that a reader arriving at the last page is left dumbstruck. In the making for over a decade, “Nureyev” unscrolls everything that matters about the sensibility, the actions, the ambitions and even the unconscious impulses of the dancer who serves as its titanic subject, and it places them in the full contexts of the theater and society of his era.

For the first time in this reader’s experience, at least, Rudolf Nureyev seems not only comprehensible but even, from the distance of a posthumous book about him, admirable. I write this while aware of the fact that he professed a virulent anti-Semitism despite several tours to Israel, where he was well received onstage and happily cruised the streets at night. However, when it came to working with Jerome Robbins, a Jew he considered a master, the anti-Semitism seems to have disappeared, and Nureyev became a lamb in the studio. Nothing, not even deep-seated prejudice, superseded his thirst for excellence and his ravenous curiosity to explore all the possibilities his art could offer.

Excitingly feral and arrestingly innocent in his early years, Nureyev purchased his experience and fame at a considerable price. Prematurely cut down in his 50s by the complications of AIDS, he died with the knowledge that he had compromised his own artistic ideals and that he had proven an emotional beast toward family, friends, lovers and colleagues. His constant performing past the height of his excellence had disfigured his audience’s memories of him at his pantherine best; his choreography was discounted as fussy and, in some cases, unwatchable. To much of the dance world that had seen him in the 1960s and ‘70s, he had become a caricature of a hero, if not a brute self-parody.

Yet thanks to Kavanagh and the many Nureyev friends, fans and family members who helped her, he emerges here even from chapters of degradation with his dignity intact — a figure of monumental stature in the mold of Byron or Michelangelo, a category-5 force of solipsistic intelligence, perseverance and charisma, whose godlike energy, intermittent capacity for human feeling and permanent legacy for the world of dance iis finally possible to understand.

Whatever you want to learn about the dancer or the man is here except, perhaps, for a definitive answer to the question of whether he and Margot Fonteyn, whom he called “the dear friend of my soul,” ever slept together. (Given the way this book is written, it would seem they didn’t.) In terms of Nureyev’s art, Kavanagh has given us the complete story — at last — of his childhood teachers and Kirov youth in the Soviet Union; a detailed and engaging portrait of his performances in the West, with qualitative evaluations as well as analyses; a chronicle of his stagings of works by Marius Petipa and his original ballets; and a study of his collaborations with choreographers, costume designers, and filmmakers. She recreates his intellect, giving a sense of his reading (Jorge Luis Borges, Gustave Flaubert, Mario Praz) and of his inclinations as a listener to music (classical, classical, classical).

She provides an account of the condition of his dance technique at every stage and of his changing attitudes toward his presentation of it in performance, and carves an informed cameo of every major dance partner, a group in which Fonteyn (whom Nureyev also described as a kind of mother) has pride of place. She opens a window on his dream projects (beginning with his hope to dance for George Balanchine) that either never came to fruition or, if they did, came too late. And — arguably best of all — she makes a running inventory of his beneficial effects on male classical technique and repertory, and constructs a rationale for the peremptory changes he imposed on inherited Petipa classics as well as on ballets by contemporaries, including, amazingly, “Theme and Variations” by his idol, Balanchine.

For The St. Petersburg Times Nureyev: The Life // By Julie Kavanagh // Pantheon Books // 782 pages. $37.50

As someone who saw Nureyev perform live in the West from the early 1960s until the late 1980s, I can say that everything Kavanagh reports about his art could be observed on stage and in film.

In terms of the star’s offstage existence, the biography is also superb. The chapters on Nureyev in the Soviet Union, prior to his 1961 defection in Paris, are particularly wonderful, having the benefit of hitherto-unknown documents (Kavanagh, who is not a Russian speaker, commissioned translations) and, for Western readers, of fresh recollections from family members, friends and fellow artists. One comes to cherish his nourishing friends in London, the critics Maude and Nigel Gosling, and to respect the honest Dutch choreographer Rudi van Dantzig, the beleaguered yet faithful agent-factotum Joan Thring, and others.

Although Nureyev said that the love of his life was the Danish virtuoso Erik Bruhn, with whom he enjoyed rich artistic harmony and stormy personal relations, and although shortly before death Nureyev commented that he should have stayed with the filmmaker Wallace Potts (“Wallace was the true one”), and although Nureyev’s parade of male lovers and pick-ups and fellow bathhouse orgiasts is innumerable, he had many women around him as well, including a small group who were sexual partners. Apparently, he asked several to bear him a child, though none did. (He, himself, spread rumors of abortions.) The women outside the theater who seem to have had the deepest effect on him emotionally were Russian: Ksenia Pushkin, the wife of Nureyev’s beloved Kirov teacher, Alexander (she initiated an affair with Nureyev when the latter was still a teenager); and Menia Martinez, a Cuban dancer in Leningrad to whom Nureyev twice proposed and who, in the interests of her own career, twice rejected him.

His seriousness with Menia, in particular, is one of his shining qualities as a human being, and Kavanagh’s descriptions of the moments between them are among the biography’s most memorable. (Martinez, Ksenia Pushkin and other Russians in Nureyev’s life can be seen — along with early films of Nureyev at the Kirov — in the touching new film “Nureyev: The Russian Years,” recently telecast in the United States.)

Wallace Potts, who, lamentably, also died young last year, headed up the U.S. branch of The Rudolf Nureyev Foundation, and his intrinsic devotion and kindness are everywhere present in this book. Nureyev seems to have written little, apart from his autograph, his early autobiography and a few letters, which, apparently, haven’t survived.

Still, he was perhaps the most completely documented dancer of the 20th century in terms of film, photography (David Daniel’s pictures from the late 1960s and ‘70s are the most beautiful), interviews, appearances in other people’s journals and dance criticism. Kavanagh’s is the authorized biography — there are many unauthorized ones, as well as published memoirs — and it is absolutely clear that the Nureyev estate, his remaining intimates, members of the dance profession and everyone else who contributed information were at one with the author’s efforts to tell his story fully and vividly, to show all of him without erasures and yet also without embarrassment: to get it right. As final songs go, it is a great one.