When NPR's Scott Simon began tweeting from his mother's hospital room in July 2013, he didn't know that his missives would soon spread well beyond his 1.2 million Twitter followers. Squeezing the magnitude of his final days with her into 140-character updates, Simon's evocative and moving meditations spread virally. Over the course of a few days, Simon chronicled his mother's death and reminisced about her life, revealing her humor and strength, and...