The year has brought Mr. Chernow experiences that he describes as “a biographer’s wish-fulfillment fantasy.”

Outside of the theater one night, actor Anthony Ramos, who plays John Laurens and Philip Hamilton, was signing autographs and spotted Mr. Chernow, “real incognito in the back,” the actor recalled.

“I wanted to give a shout out to Ron,” Mr. Ramos said. “If it hadn’t been for him, we wouldn’t be here.”

So, putting the author in the stage-door spotlight, he yelled: “Everybody, this is the guy who wrote the book!”

The scrum gasped and swiveled, applauding a man accustomed to tidy lines of fans at book stores.

“I was so startled by the crowd’s reaction, I simply waved and rushed off in a daze,” Mr. Chernow said, estimating there were 150 people. “I had never had a moment like that.”

The moment was unique not only because of the “demonstrative” fans, he said, but also because he had incorrectly imagined the cast would be full of feuding stars and prima donnas: “They’re all so damn nice. There has been very little backstage drama.”