Before they spearheaded the musical phenomenon called "the British Invasion," John Lennon, Paul McCartney, George Harrison, and Ringo Starr were just four kids from Liverpool. Throughout the 1960s, however, they embodied, as the Beatles, the musical, artistic, social, and spiritual promise of an entire generation. After their stormy breakup in 1970, the Fab Four became four solo artists, at times even appearing on each other's recordings. In addition...