"We've always said the point of all these things is to understand our history better, understand our culture better. When you read something really interesting or when you encounter a provocative decision, it's a conversation-starter. That happens with influential books, with influential speeches, or any form of culture."

 Johnson, who is the author of Everything Bad Is Good for You, is something of an agent provocateur for popular culture in general and video games in particular. He contends that any generation is comfortable with the forms it knows and reluctant to acknowledge new ones. He does a "what-if."

 "Imagine an alternate scenario where games had been invented three hundred, four hundred years ago and they've been played for years and our whole institution is devoted to celebrating them and, and all of a sudden books were invented and they were all the rage for your kids." Grown-ups would be dubious about the new craze.

 "So I came up with all these criticisms about books." He offers a tongue- in-cheek rundown: "They're socially isolating. They discriminate against people with dyslexia. They force people to follow linear thoughts that somebody else has dictated in advance. They're teaching people to follow the plot instead of teaching them to lead, to make decisions."

 A report by two professors from the University of Illinois and the University of Wisconsin finds some agreement with Johnson's thesis. It sees multiplayer games as promoting social networking, much like pubs and coffeehouses.

 Johnson believes that books and games and blogs can happily coexist. Everything Bad was done as a book, he points out, and he has just published another one, The Ghost Map, a nineteenth-century detective story about a cholera outbreak in London.

 From today's technological revolution, we turn back eighty years to another revolution, this one musical. The setting is America between the world wars, a time for a freer look, freer behavior, freer music. Jazz, once the providence of smoky New Orleans clubs, had become a national phenomenon. For an older generation that revered classical music, jazz's freewheeling melodies and penchant for improvisation sounded heretical.

 We visit the lives of two men-one a well-to-do composer crossing the Atlantic from Europe with the cacophony of Paris still in his ears, the other a kid from Pennsylvania whose entrée to the world of music was through a Pittsburgh numbers runner. George Gershwin returned to his home on the Hudson and resumed work on a piece that became An American in Paris; Billy Strayhorn found a spare bed in Harlem at the home of the bandleader Duke Ellington and began a musical collaboration that lasted nearly thirty years.

 By the 1950s, jazz had become so integral to American culture that musicians such as Dave Brubeck and Louis Armstrong traveled the world as jazz ambassadors. Whether it was swinging or calculatedly cool, to the men and women behind the Iron Curtain, jazz sounded like freedom.

--Mary Lou Beatty