A comprehensive list of significant voices in contemporary music would include Franghiz Ali-Zadeh of Azerbaijan, Chen Yi of China, Unsuk Chin of South Korea, Sofia Gubaidulina of Russia, Kaija Saariaho of Finland, and Pauline Oliveros of the United States. Composition has also ceased to be exclusively male; the preceding six composers are all women.Ross must know that composition has never been exclusively male. What was he thinking when he wrote that statement?
Since Ross doesn't say anything in the book about Ali-Zadeh, I'm putting a link to her here (this is also the first I have heard of her). Unsuk Chin is named on Ross' list, but like Ali-Zadeh her only reference in the index is to the list of women on page 516. Kaija Saariaho made it onto two lists: one of women and the other of Finns, but there is nothing in the book about her music or the music of Chen Yi.
To his credit, Ross does have part of a sentence about Pauline Oliveros on page 492, which she shares with Morton Subotnick, and he does write a bit about Sofia Gubaidulina, though mostly in relation to the circumstances of Shostakovich's life in Soviet Russia. He does, however, devote nearly a whole paragraph to Gubaidulina, and in it he (very briefly) describes two of her pieces.
Aside from a few references to performing musicians (Billie Holiday, Björk, and Bessie Smith, for example), all the rest is men.
For another review of the book I would suggest Charles Shere's view from the Eastside.