Certain questions and comments tend to recur, I've noticed, in talking about Cleopatra. Many have come as complete surprises. For example, I've signed countless books for fathers who wanted to pass them on to daughters, who they hoped would prove to be—or who were on their way to being—powerful women. I hadn't seen that at all, either in thinking about the book or in writing it. It thrills me of course, not only because I have two daughters; over and over it has been said that the single most crucial factor to a woman's success is a father who took her seriously—as Cleopatra's father clearly did her.

A sampling of FAQs follows, in some cases along with answers.

MOST FREQUENTLY ASKED QUESTION: Who did she love more, Caesar or Antony?

I'm not convinced she loved either. Sovereigns like Cleopatra thought in terms of affairs of state rather than of the heart. And strategically speaking, she was in a difficult position from the minute she came to power. There is evidence of affection for both men, above and beyond the political alliances and the gaggle of children.

QUESTION I WISH I COULD ANSWER BUT CAN'T: Her subjects thought of her as a goddess. Did Cleopatra believe herself one?

QUESTION REQUIRING THE MOST TACT: Did you meet her?

MOST DIFFICULT QUESTION: What modern woman most resembles Cleopatra?

I always feel I'm meant to say Sarah Palin or Hillary Clinton. Generally I come down closer to Oprah: a brainy, enterprising woman with one name who controls an empire and instinctively knows how to command an audience.

FAVORITE QUESTION: What about the snake?

Disentangling Cleopatra from the deathbed asp speaks volumes to how history (and fiction) get written. I've called Cleopatra's snake the cherry tree of ancient history. It's a convenience and a shorthand—and surely a falsehood.

QUESTION I'M ALWAYS HAPPY TO ANSWER: How did you know where the book opened?

As soon as I set foot in the desert near where Cleopatra had camped—exiled, at 20, and with an army she had singlehandedly raised—I knew that was where her story started. Here was a different queen from the one we assumed we knew.

MOST AMUSING QUESTION: Did they pay you extra for posing for the cover?

QUESTION THAT CONTINUES TO ASTONISH: Did you have any idea the book would resonate as it has with modern readers?

In a word, no. As my friends and family would all too eagerly attest, I spent four years complaining, worrying, and not sleeping. When I wasn't doing that I was apologizing for my choice of subject. Generally the conversations went like this: "What are you writing about?" "Don't laugh—Cleopatra."

QUESTION ONLY ASKED FROM A FRONT ROW SEAT: Do you have any advice for the aspiring biographer?

Leave as much as you can on the cutting room floor. The biographer has been said to lower a small bucket into a great ocean of material; allow a lot to slop over the edge. Remain skeptical, of documents as much as memories. Joan Didion reminds us that in keeping a journal she has "always had trouble distinguishing between what happened and what merely might have happened." Talk to everyone who knew your subject, in any context. Keep him or her front and center—and in trouble whenever possible. We want always to know what he's thinking. The book will take a year longer than you think. And people will forgive you if you misdate your checks—with the wrong century.