Kevin Costner has been a leading man for more than 40 years and has starred in many different genres of movies, but a constant in his filmography is the Western. His latest project, “Horizon: An American Saga,” a series of four films about the founding of a town in the West, has been in the making for decades. Costner joins David Remnick on Radio Hour to talk about the current state of Hollywood and how “Field of Dreams” became “our generation’s ‘It’s A Wonderful Life.’ ” Listen to the full epis