Antony Sher, one of the most prominent British stage actors of his generation, is currently making only his second visit to Broadway. The show he’s starring in was a hit in London, but – by his own choice – he’s performing it here only 32 times. He has good reason.

“The producer had huge problems with my inability to do it for a proper season,” he admitted. “It’s purely because I can’t do it as long as one might do an ordinary play.” Indeed, “Primo” is no ordinary play. It is Mr. Sher’s 90-minute, no-intermission, one-man adaptation of what many consider the preeminent literary document to come out of the Holocaust, Primo Levi’s “If This Is a Man.” Levi published the memoir in 1947, not long after being liberated from Auschwitz.

“I’ve played some of the really big Shakespeare parts and classical parts, and they are taxing in different ways,” continued Sher, 56. “And often they are marathons in the sheer length of the pieces. Now, this is only an hour and a half, but it is me alone speaking, and it is about material that is uniquely harrowing and upsetting and – strangely enough – inspiring, because it is about survival and not destruction. Now, that is – I don’t want to sound precious, because people always accuse actors of being precious – but it is quite hard to go through again and again.”

Mr. Sher’s adaptation is the most austere imaginable. The actor, like many others before him, objected to the notion of staging the Holocaust. His Primo Levi is a free man in glasses and comfortable street clothes, relating his experience in a voice as regulated and moderate as that found in the book. He briefly erupts into anger only twice during the monologue – once when reacting to the casual cruelty of a Nazi, the other time at the selfish prayer of a fellow prisoner. Yet even these “gusts,” as Mr. Sher calls them, are the outbursts of a thinking, reasonable man.

“That’s Richard Wilson,” explained Mr. Sher, mentioning his director. “It’s he who had a vision of how to do this. Though I adapted it, I didn’t have a vision of how to do it. We watched documentary films of real survivors talking, like the great documentary “Shoah.” And then we met real survivors, as well, who came into the workshops to talk to us. There was one woman in particular, called Trudi Levi – no relation – who talked with such restraint and yet was so full inside. There was something about that combination of her having been to hell and it being so inside her that she just needed to tell us, rather than demonstrate in any emotional, histrionic way. It was both seeing those people in the documentaries and then being in the same room with this woman that made Richard Wilson say ‘That is what they’re like. That is how we have to do it.'”

Antony Sher first encountered “If This Is a Man” in 1989 while working on the Peter Flannery play “Singer,” which begins with a scene in Auschwitz. Though inwardly troubled about the idea of creating a three-dimensional version of the Levi’s account, he completed a draft of what would become “Primo.” He did not know that the author’s estate had decreed that the book would never be adapted for film or theater. Mr. Sher’s respectful approach, however, eventually won over the executors, including Levi’s son Renzo.

The actor retains an air of solemn deference when he discusses the project, speaking in exact and deliberate cadences, as if fearful of breaching the proper tonal etiquette. This is somewhat remarkable, because Mr. Sher is not a man without conceit. He rose to fame not so much for essaying a famous Richard III in 1984, but for following it up with “The Year of the King,” a well-read memoir of the experience. He remains a “compulsive diarist,” and has published an autobiography and a second memoir, “Primo Time,” about the Levi project.

Yet, in discussing “Primo,” he is uncharacteristically bridled in his language, not even allowing himself to call the work what it is: a critical success and one of the undeniable high points of his career. “It’s more than career,” he argued. “It’s been a life experience. It’s gone way beyond theater. It’s more important than anything I’ve done. There is something about the material, and that I was given responsibility to perform the material. I think what’s remarkable about Primo Levi’s book is he somehow takes the reader by the hand and says ‘Come. I’m going to guide you round hell.’ And then he does so with astonishing detail and curious humanity.”

“My job with this piece is to do a similar thing with the audience. That ‘Richard III’ experience had been a particularly important one, because it transformed my career. This has been important, because it’s been a remarkable event in my life.