Around that time, Mantel’s health began to deteriorate. A doctor dismissed her symptoms as a bid for attention and referred her to a psychiatrist. The psychiatrist gave her tranquilizers and an antipsychotic drug and told her to stop writing.

Years later, when Mantel and McEwen were living in Botswana, she researched her symptoms and diagnosed herself with endometriosis. Doctors confirmed her suspicions, and when she was 27, she had surgery to remove her uterus and ovaries. The pain didn’t abate, and Mantel suffered from complications that still afflict her: her weight increased, her legs swelled, she felt exhausted and alien to herself.

Her illness made a normal day job impossible: “It narrowed my options in life, and it narrowed them to writing,” she said.

Mantel finished her first book, a novel about the French Revolution titled “A Place of Greater Safety,” in 1979, and sent it to publishers and agents, but no one wanted a 700-plus page historical novel by an unknown writer. She wrote a second book, a brisk, darkly comic contemporary novel, “Every Day Is Mother’s Day,” which became a critical success when it was published in 1985.

Over the next two decades, she published seven other novels and developed a cult following. Though her books vary in their subject matter, style and tone, they are bound by recurring themes: her fascination with transformation and the unseen realm, with myths and archetypes.

When she was writing her novel “Beyond Black,” about a medium who channels the voices of the dead, Mantel realized she was creating a road map for the Cromwell trilogy. “I was thinking, this isn’t just about a medium,” she said, “it’s about how to induce the necessary frame of mind to let the past enact itself.”