HIS hair was going, his ears like handles, his jaw dropping and his personality bland. But Fred Astaire's bosses at RKO Pictures saw past all that. "Make perfection," they told him, and that is what he did – so much so that, 70 years later, those films – among the most inane masterpieces delivered by any culture or genre – still look superb.

RKO's musicals were irrelevant upper-class fables with the sketchiest plots, a string for the pearls of dance routines married to some of our best popular songs. Epstein's book is a very readable and glowing 50,000-word portrait, notwithstanding his determination not to subject Fred to rough cross-examination or prolonged background scrutiny. But if you're introducing Astaire to a novice, know that this book not only rejects depths to explore, it prefers to believe they do not exist. Further, Epstein seems to assume you can't really describe a dance routine and settles for a few potent, impressionistic touches. An Astaire virgin might do better to buy a DVD of Top Hat or Swing Time or even Silk Stockings. With Astaire, the vital lesson lies in seeing what he does and then realising how determined he is to make it seem effortless. That ease is directly linked to the daft stories, which don't bear thinking about. The omission is all the plainer as one comes to Epstein's excellent commentary on Astaire the singer.

Better still, the fan or the inspired newcomer needs to hunt down John Mueller's Astaire Dancing (1985), a big volume that analyses his every dance number on film; there we learn that, in the years at RKO, the Astaire-Rogers films more than doubled in cost without showing the same expansiveness in income. I stress that because it's clear from Mueller's book just how completely Astaire was involved in every last bit of these films. The flagrant emptiness of the material, the wistful sweetness of the songs and the implacable elegance of the routines (with a camera trained to photograph the full figure) all come from Fred, who could never persuade himself he was a good enough dancer or give up the dream of becoming just a dance director.

Where did this all spring from? Epstein asks that several times, but of course he knows it didn't come from Omaha, from his German origins or a mother who took Fred and his sister Adele on the road very early. It came from inside Fred, where movement took away so many other appetites. Yes, he liked golf and horse racing and great clothes, but it's hard to picture Fred eating, let alone pursuing the other sensual tastes. When he tried to act in later films (such as On the Beach), he revealed his own ghostliness. By contrast, Ginger Rogers was a funny actress, easily able to deal with levels of sexual innuendo that were wasted on Fred.

The problem is not that Fred and Ginger never had an affair. It's that they danced together for years without altering the cast-iron, chilly smile Fred acquired when dancing with his sister.

Astaire is never going to be "rescued" for a trashy age by the revelation of a sordid private life. At the same time, his terrifying concentration and his refusal to acknowledge certain appetites lead to a conclusion seldom reached about performers in ballet or other musical forms: Fred Astaire was not human, not sexual, not sexed. But in his total disregard of the hardship and squalor of the 1930s, he let it be known that art need have nothing to do with life. That's where Citizen Kane betrays itself. It is heavy-handedly about "America". Top Hat and the others are strolls through Arcadia.

• Books editor David Robinson selects a book review every Monday.