He starts, naturally, with the most famous political convert in modern American history: Whittaker Chambers, whose 1952 book, “Witness,” documented his turn from Communism. “I read it. It was miraculous. Extraordinary hero-journey of this fellow that had to examine everything he believed in at the great, great cost—which is a cost I’m not subject to—of abandoning his life, his sustenance, his friends, his associations, and his past. And I said, ‘Oh my God. . . . Perhaps it might be incumbent upon me to see if I could get my thought and my actions into line too.”

There were other books. Most were given to him by his rabbi in L.A., Mordecai Finley. Mr. Mamet rattles off the works that affected him most: “White Guilt” by Shelby Steele, “Ethnic America” by Thomas Sowell, “The Instincts of the Herd in Peace and War” by Wilfred Trotter, “The Road to Serfdom” by Friedrich Hayek, “Capitalism and Freedom” by Milton Friedman, and “On Liberty” by John Stuart Mill.

Before he moved to California, Mr. Mamet had never met a self-described conservative or read one’s writings. He’d never heard of Messrs. Sowell or Steele. “No one on the left has,” he tells me. “I realized I lived in this bubble.”

When it popped, it was rough. “I did what I thought was, if not a legitimate, then at least a usual, thing—I took it out on those around me,” Mr. Mamet says wryly. It took “a long, long, long time and a lot of difficult thinking first to analyze, then change, some of my ideas.”