STRATFORD-UPON-AVON, England — When Hilary Mantel was writing “Wolf Hall” and “Bring Up the Bodies,” her best-selling novels about the court of Henry VIII, she was so scrupulous about accuracy that she created a card catalog of dates and events to ensure that her characters were never out of joint with the past. But when the Royal Shakespeare Company began cutting her 500-page books into two-and-a-half-hour plays, Ms. Mantel had to act as “the history police,” as she put it.

She could live with sacrificing moments where her main character, Thomas Cromwell, Henry’s powerful adviser, fought with Thomas More and other ministers over the king’s plans to marry Anne Boleyn. But a moment of truth came when someone suggested streamlining the royal marriage by having Henry turn against Anne when their first baby wasn’t a male heir. “You would like history to be more convenient, but once you say ‘We’ll just fudge that,’ it’s a slippery slope to ending up with no credibility,” said Ms. Mantel, who made her own history by winning the Man Booker Prize for a novel (in 2009 for “Wolf Hall”) as well as for its sequel (in 2012 for “Bring Up the Bodies”).

“I had to draw the line, though I sympathized,” she said. “These books have been beasts to adapt for the stage.”

The two plays, now in preview performances here, have clearly profited from the books’ popularity: Most seats sold quickly after going on sale last spring. Famous actors usually drive that kind of box office success, but in this case, the star, far offstage, is Ms. Mantel, who was widely acclaimed by reviewers in Britain and the United States for her vividly drawn characters, suspenseful plotting and lyrical prose. While no official plans have been announced, the producers are eyeing a transfer of the plays to London this year, then perhaps to New York.