She seems to see how ballet is dependent on society at large, on its surrounding civilization, and that's my own basis.
My sense, as I'm reading "Apollo's Angels," is that there is no society-at-large or history to it. Jennifer Homans' thesis seems to be that ballet is a sublime mechanism existing outside everything else. Her book, while a smooth summary of other researchers' work, doesn't itself dig into the girt of history or argue with and evaluate its sources - as Lynn Garafola often does. In Homans' telling, ballet history moves on a single homogenous trajectory (like the adagio movement of Symphony in C, or Diamonds?) - in which everything keeps getting better, albeit with some reversals, until the death of Balanchine, and then everything falls apart.
There are also very strange ways of reading things - for instance Homans cites a "prominent writer" of the era of Louis XIII - XIV, a period when there was probably no such concept, and goes on to characterize the brilliant memoir writer Duc de Saint-Simon, as "himself a virtual patron saint of ambition and spleen" and then hardly uses him - or Madame de Sevigne' - as eyewitnesses.
And while not mentioning the development of Cuban ballet at all - as Natalia has previously noted, Homans curiously remarks that “Dancers from Russia and the former Soviet bloc, as well as Cuba and South America, are flocking the the West.”
Regarding Diaghilev, "Apollo" - the ballet of the title - rates only two pages of analysis and "Prodigal Son" is not mentioned at all. Both are significant end points for the Ballets Russes ("Apollo" can be looked at as a remake of "Afternoon of the Faun," all its excesses corrected, and "Prodigal Son" burlesquing and then purifying early Ballets Russes Orientalism). "Parade," a significant mid-point ballet, subject to much scrutiny these days by art historians such as Yve-Alain Bois and Elizabeth Cowling, is not taken seriously.
Another odd comment: "Degas' intense preoccupation with ballet - almost half his work focused on ballet - was evidence of the art form's lasting ability to mirror its times." The other half or so of the famously grumbling misanthropist Degas' work is, unfortunately for this comparison, that of the brothels, which according to the art historian Theodore Reff, was "a subject imbued with that melancholy spirit of isolation and disillusionment which Degas and Huysmans identified with a modern sensibility. [They were] drawn by nature to the closed, nocturnal world of urban entertainment and distraction, rather than the sunlit one chosen by their Impressionist colleagues."
The balletic world that is reflected in Degas is of odd and cool alliances between patrons, mothers and dancers. His paintings are made up of small isolated drawings, as repetitious as barre work, that finally are tacked together, like a series of fruit on an espaliered tree - borrowing Degas' own metaphor. Jules Perrot - whom Degas genuinely admired - is moved about like a chess piece among the girls and mothers and stray cats and stray men in high hats (there are no male dancers at all in Degas' world).