Though the title claims to only cover one century, Mackintosh begins by going back to 1870 and the planning of Richard Wagner's Festspielhaus in Bayreuth. Seating for the theatre was to consist of a giant fan shape surrounding a massive proscenium stage and sunken orchestra pit. Originally, there was no elevated mezzanine or balcony, though an upper level was added later. A fan-shaped auditorium works for Wagner's epics, but Mackintosh argues it can be deadly when applied to lighter operas such as those by Mozart.
The book then takes a detour through an even older theatre, the Festival Theatre Cambridge, which was originally designed by William Wilkins in 1814. I had a chance to visit the theatre (now a Buddhist center) back in 2016 at a conference on Regency-era drama held by the Society for Theatre Research. In the 1920s, Terence Gray acquired the theatre and remodeled it, but left intact some of the original stage machinery. Later, he offered Gordon Craig the chance to take over the theatre, have complete artistic control, and do whatever he wanted, but Craig demurred.
Mackintosh treats the older theatre extensively because it illustrates his point that an old-fashioned horseshoe-shaped wraparound suspended over the orchestra seating provides better intimacy than Wagner's giant fan, which has proved so influential. He argues that the thrust stages pioneered by Tyrone Guthrie provide a better alternative to a fan-shaped auditorium, like that of the Olivier at London's National Theatre. When I saw the brilliant musical Hadestown in the Olivier, I was disappointed, especially since the show had been so enjoyable in the much smaller space of New York Theatre Workshop. According to Macintosh, however, almost nothing works in the massive Olivier, which has a stage far too wide and audiences inevitably stretched out far from the action.
Fan-shaped theatres frequently have poor acoustics, in spite of being modeled on ancient Greek stages that can have excellent acoustics when used properly. Mackintosh argues that the massive theatre at Epidaurus is larger than those used by the great classical dramatists of Athens, and was later more than doubled in size by the Romans, who preferred watching spectacle to listening to poetry. Rather than using the fan layout of the Greeks, Mackintosh prefers theatres like London's Barbican, which uses multiple wrap-around levels to fit the whole audience into a smaller area, making sure no one is positioned too far away from the stage.
The book is also kind to historical reconstructions, such as Shakespeare's Globe and the smaller Wanamaker Playhouse attached to it. When the reconstructed Globe was opened, some purists thought it would just be a tourist trap, but in spite of not receiving the large subsidies enjoyed by the National Theatre, Shakespeare's Globe offers cheaper tickets than the NT, and continues to attract young audiences who prefer its uncomfortable seats (or worse yet--standing room) to the comfortable but pricey seats in the Olivier.
Mackintosh also chronicles efforts to save historic theatres, including the Theatres Royal in Bristol, Bury St. Edmunds, and Richmond Yorkshire. When the theatre in Dunfermline, Scotland couldn't be revitalized, its interior was shipped to Sarasota, Florida, where it graced the home of Asolo Rep. Some other theatre cultures were not so fortunate. In a later chapter, the book discusses the wholesale destruction of traditional theatres in China during the Cultural Revolution.
Perhaps a vindication of Macintosh's preference for wrap-around seating is that the Royal Shakespeare Company modified their main theatre in 2010 to provide a thrust stage. I remember seeing a production of As You Like It in the old theatre there in 1996 and being unimpressed. Overall, I think Mackintosh makes a good case.