Letterman Had An Impact On The Way People Understood Comedy

President Barack Obama with host David Letterman smile during a break at a taping of CBS The Late Show with David Letterman at the Ed Sullivan Theater in New York, Monday, May 4, 2015. Obama traveled to New York to announced the creation of an independent nonprofit organization that is a spinoff his "My Brother's Keeper" program, to tape a segment on Letterman's show and to do fundraising for the Democratic party. (AP Photo/Pablo Martinez Monsivais)

Dean Richards talks with author Jason Zinoman about his book Letterman: The Last Giant of Late Night. They discuss David Letterman’s legacy in late-night TV and how he distinguished himself as a new kind of talk show host.

What is your favorite memory of David Letterman?