Imagine a road trip across the United States with a voracious friend who eats, sleeps, and breathes music, listening to an endless supply of mixtapes and local radio stations devoted to everything from honky-tonk to underground hip hop, from post-punk to electronica, from teen pop to alt-folk. In the middle of the night, driving, say, through the cornfields of Iowa, or over winding mountain passes in the Rockies, after each song, your friend delivers impassioned impromptu mini-essays locating the lyrics and rhythms in the context of the last thirty-five years of American music. This is what it’s like to read