When is the right time for an artist to step back and look at the life and work he has created? For Jeff Tweedy, leader of the rock group Wilco, it was when someone offered him a book deal.

Writing his memoir, “Let’s Go (So We Can Get Back),” the 51-year-old came to better understand what has sustained him throughout his career, including a compulsion to create and the thrill of exposing raw emotions through song.

Mr....