An epic achievement and a huge delight, the entire history of popular music over the past fifty years refracted through the big genres that have defined and dominated it-including rock, country, punk, R&B, dance and hip-hop-woven together into a cosmic reckoning with music's evolution as a popular art form, as a huge cultural and economic force, and as an essential component to our identities, from Black Sabbath to Black Flag to Beyoncé, and beyond. From his own adolescence, when his allegiance was to punk rock, to his work as one of the essential voices of our time on music and culture at the New York Times and the New Yorker, Kelefa Sanneh has made a deep study of how our popular music unites and divides us, the tribes it forms, and how its genres, shape-shifting across the years, give us a way to track larger forces and concerns. Music is also, of course, a perfectly fine concern in itself, especially in the hands of a writer this brilliant...