Karen Mack, co-author with Jennifer Kaufman of the new historical novel Freud’s Mistress (July 9, Amy Einhorn/Putnam) says simply and without hubris: “After three years of researching and writing this book I don’t think any Freud scholar would know more than we do about his personal life.”

Freud’s Mistress is a fictionalized account of the love affair the controversial psychiatrist had with Minna Bernays, his wife’s sister, who moved in with the family in Vienna in 1895 and remained a member of the household for the next forty years. Mack, a former attorney and longtime TV producer and Kaufman, a journalist who is a former staffer for the Los Angeles Times and Women’s Wear Daily, were inspired to write the novel after learning that in 2006 a German sociologist finally found proof that Freud did, indeed, have a scandalous affair with his sister-in-law during the very years he was formulating his most important psychological theories. The century-old hotel log the sociologist discovered in Switzerland shows that Freud, traveling with Bernays, registered for a single room with one double bed as “Dr. Freud and Frau.” This was all the evidence Mack and Kaufman, who have co-written two other novels, needed to begin writing Freud’s Mistress, which required they travel to London for a research visit to the Freud Museum and house, and also hire a German translator so they could read the more than 300 letters written by Freud before his death in 1939 and now stored at the Smithsonian in Washington, D.C.

Although they have different strengths as writers, Mack and Kaufman seem to work in such a seamless collaboration that it’s hard to believe Freud’s Mistress was a joint effort. “As a journalist I’m more into descriptive prose,” Kaufman says, “and because she works in TV Karen’s more into dialogue, characterization, and organizing a story. Obviously we used our strengths, but that changed very quickly and we both started doing everything.” One of the challenges the pair faced in writing historical fiction for the first time was in making the facts in the story “organic. So we had to revise and rewrite until it became natural,” Mack says. “But it was all research, and we lost the story. The first draft was like a biography.” When their editor Amy Einhorn read it, she was enthusiastic about Freud’s Mistress but felt the novel needed more exposition and more facts. The co-authors then had to rewrite the book again, starting from the beginning as storytellers.

Considering that Mack and Kaufman didn’t visit Austria to research Freud’s Mistress, it is to their credit that the novel authenticates fin de siècle Vienna in such detail. “When Freud fled Vienna because of the rising anti-Semitism, everything in the house went with him to London, all the papers and artifacts. So we went there instead,” Kaufman says. The authors also researched maps, photos, and films, and read all the related books they could find – including old Viennese cookbooks.

In his sister-in-law Freud found both intellectual and sexual fulfillment. “Of course the book is about the affair, but it’s also about two sisters, one who usurps the other’s life – her husband, children, and lifestyle,” Mack says. It is unknown whether Martha Freud was ever aware of the affair between her husband and sister, although in Mack and Kaufman’s hands the household, including the six Freud children, seems to have amicably worked out the living arrangements and various relationships under one roof. “This story sheds so much light on Freud’s work and his theories. You wonder how the affair affected his ideas,” Mack says. “If a Freud scholar were to look at him through the prism of what was going on in his life at the time, it would be very interesting.”