Since before Melvil Dewey invented his decimal system in 1876, there has been the urge—even the need—to categorize books. This is a hurdle for those who write, publish, and sell books that are not easy to classify, such as my upcoming book, Inga: Kennedy’s Great Love, Hitler’s Perfect Beauty, and J. Edgar Hoover’s Prime Suspect.

Much as Hollywood spits out sequels to successful films, the publishing industry likes what is tried-and-true and easily understood. I learned this with my first book, Almost President: The Men Who Lost the Race but Changed the Nation, when I noted in my proposals to prospective publishers that no one had ever done a book quite like it before. Wrong approach, I was told. Instead, the key to a good proposal was to identify books that had sold well and were similar to mine. Then it would be possible to understand and find the target audience.

“People like to read about people,” a wise editor told me, so I retooled the book, making it less a meditation on losing and more a series of short biographies of losing presidential candidates who still influenced American history. But the problem remained of where to shelve such a book: U.S. history, political science, biography, or current events? Fortunately, the book was well reviewed, so it sold well, even though it might have been hard to find.

I didn’t learn my lesson. Having written about losing, I wanted to write about two of the greatest winners in American politics: John F. Kennedy and Ronald Reagan. My thinking was that we could learn something new by taking a fresh approach to a familiar subject—but by doing what I called a “comparative biography,” I again made marketing difficult.

Where do you put a book titled Kennedy and Reagan: Why Their Legacies Endure? In biography under K, for Kennedy, or R for Reagan? Usually neither, I found out, and the categories chosen by booksellers were even more varied than they were for Almost President.

So for my third and newest book, I decided to focus on just one person, but it turns out this one is tough to categorize too. It’s the story of Inga Arvad, Miss Denmark of 1931, who was an actress, a foreign correspondent, an explorer who lived among tribes in the East Indies, a Washington reporter, a Hollywood gossip columnist, and a screenwriter for MGM. She was adored by Adolf Hitler and John F. Kennedy wanted to marry her.

Arvad’s historical significance is that she was perhaps the love of Kennedy’s life: they shared a romance at the beginning of World War II. But because she had been shown favor by Hitler while she was a journalist in Nazi Germany (and also because of the not inconsequential detail that she was still married to her second husband, filmmaker Paul Fejos, whom Charlie Chaplin considered a genius), Arvad and Kennedy’s relationship faced all sorts of complications.

The FBI suspected Arvad of being a Nazi spy and put her under surveillance, tapping her phone, bugging her apartment, and recording her most intimate encounters with Kennedy and others. This nearly led to Kennedy, then an officer in Naval intelligence, being court-martialed. Instead, it set in motion a chain of events that led to Kennedy’s eventual transfer to the South Pacific, where he became the war hero that made his political career. As he recovered from the sinking of the PT-109, Kennedy continued to pine for Arvad and hoped one day to marry her. That, of course, did not happen.

Arvad’s is a remarkable story, and I hope I have told it well, but now I wonder how readers will find it. It’s a little about Hitler and the Nazis; a little about Hoover, F.D.R., and civil liberties; a little about Hollywood during the war; a lot about Kennedy, his family, and how he became a politician; and all about Arvad, a woman no novelist could invent.

So where will Arvad be displayed? In biography, alongside books on the Kennedy presidency, or even in women’s studies? There is no obvious cubbyhole to place her—which is the magical aspect of her life.

Until a new shelf is created, called “Remarkable Women We’ve Never Heard of Before,” my solution is that booksellers feature her in the front store windows or the front page of their websites. For any author, undeniably, front and center is the best category of all.