In the late '90s, no flop was really going to kill U2's career, but Pop was cause for concern. Following Zooropa (1993) and Achtung Baby (1991), the album capped a trilogy that saw these venerable stadium gods reinvent themselves as electro-rock experimentalists. The songs are built around loops and samples, and while the band had made successful use of such techniques, Pop suggested that Bono and the boys had run out of ideas and reached the end of a particular phase of their career. The public more or less agreed, and Pop became U2's lowest-selling disc since 1981's October.

Having perhaps learned their lesson, U2 returned three years later with the more guitar-centric All That You Can't Leave Behind. The album spawned four smash singles and won seven Grammys, and to date, it's sold more than 12 million copies.

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