Let’s turn to the books, starting with the memoir of the American playwright Moss Hart. What do we learn about bygone Broadway and the glamour of its glory years by reading Act One?

Act One may be the greatest show-business autobiography ever written. It's certainly one of the greatest. The book is a compendium of backstage stories and anecdotes about all the fabulous people Moss Hart knew intimately – and he knew them all. Hart co-wrote some of the most successful comedies in Broadway history with George S Kaufmann. You Can't Take It With You and The Man Who Came to Dinner are probably the most famous – you still see them being revived today. Hart also directed many successful shows including My Fair Lady, one of Broadway’s biggest musical hits.

But none of that is covered in Act One, and you don't really care. The book is a funny, heartfelt description of Hart’s struggle to make it big on Broadway in the 1920s. He grew up poor in the Bronx. Even though Hart’s family couldn't afford food, his aunt always found a way to go to the theatre. She'd come home and describe in detail everything that she saw on stage. She must have been a great storyteller, because Hart became obsessed with Broadway.

He writes that “the theatre is not so much a profession as a disease”, and offers a theory about who is particularly susceptible to infection.

Hart talks about Broadway as a refuge. Certainly that's how he looked at it, as a magical place where the troubles of the world no longer matter. These days you may wonder what possesses people who are drawn to theatre, because it's not the major American cultural force it once was. But there's something about live performance, and the glamorous history that Hart writes about, which still attracts people to Broadway.

Let’s move onto The Season by William Goldman. Please tell us about this portrait of Broadway. What can we learn about how American commercial theatre works from reading it? Why is still relevant today?

This book is an exhaustively researched assessment of a single Broadway season in 1967-68. He interviewed pretty much everyone involved with every show. The book is useful even today, because it analyses every production that opened that season and uses each to illustrate a different point about Broadway, the various forms of theatre, and the economics of putting on a show. He also shows how difficult it is to make money. Most Broadway shows never turn a profit, which makes it a very strange business but for the fact that a lot of people make money on shows that don't return the investment of their producers.

Some of what Goldman has to say is dated. For instance, he puts forward the notion that William Inge, Tennessee Williams and Edward Albee – who were all gay – didn’t do a good job of writing about relationships between men and women, which is absurd. But aside from the anachronistic attitudes that crop up, the writing is frank, funny and entertaining. You get a sense of what was going on backstage. It’s really compelling.

The Season covers a transitional moment in Broadway history. What was changing, and what has changed since then?

It was written at a time when the influence of Broadway on American culture had already begun to wane. In an early chapter he notes that the movie The Graduate, which opened during this period, out-grossed all of Broadway theatre during that season.

Through the 50s, the theatre maintained its importance in American culture. But by the late 60s, the culture was being upended. Producers and writers were desperately trying to figure out how to either find new audiences or keep the audience they had left. Some of the shows produced during that season – comedies about counterculture and the generation gap – reflect that desperation. Jean Arthur, an old-time film actress, appeared in one show called The Freaking Out of Stephanie Blake, about a spinster from the sticks who comes to New York to rescue her niece from hippies. Apparently, it was as shockingly bad as it sounds. I think it never even opened. But there were a few shows like it that season.

Plays were already in danger, they were already having shorter runs. The long runs of successful musicals was a phenomenon that was just starting with Fiddler on the Roof, Hello Dolly and Man of La Mancha. A decade or two before, a long-running musical like Oklahoma! only lasted for a few hundred performances. These days, musicals run for five, eight, 10 years.