From his allegiance to punk rock in his adolescence to becoming an essential voice on music and culture, Kelefa Sanneh makes a deep study of how popular music unites and divides us. Distilling a career''s worth of knowledge, he explores the tribes music forms, and how its genres, shape-shifting across the years, give us a way to track larger forces and concerns.This is a book to shock and awe the deepest music nerd, and at the same time to work as a heady gateway drug for the uninitiated.