Few, if any, historians have brought such insight, wisdom, and empathy to public discourse as Jill Lepore. Arriving at The New Yorker in 2005, Lepore, with her panoptical range and razor-sharp style, brought a transporting freshness and a literary vivacity to everything from profiles of long-dead writers to urgent constitutional analysis to an unsparing scrutiny of the woeful affairs of the nation itself. The astonishing essays collected in The Deadline...