"Show me a magazine (these days) that can sell with Madonna on the cover," challenges Kaplan. "Except for maybe a Rolling Stone, Madonna does not sell. She does much to be unlikable. People don't like her penchant for taking off her clothes in public; they don't like her attitude. She may be a billionaire, but all I can testify to is that she is not a cover name.
"I can't explain it," he adds. "All I can tell you is that Princess Diana is the leader of the pack."
Publisher Steven Schragis, whose Carol Publishing Group owns Birch Lane Press, says that until "Diana in Private," the most successful book he had published was 1989's "A Woman Named Jackie"--a tell-all about the former Queen of Camelot--which spent 22 weeks on the bestseller list.
"The hardcover book-buying public is exactly the public that matches this subject: women more than men, women with time on their hands, older rather than younger," Schragis says, noting, "There are very few people where there's a total fascination about what they do." The only other celeb who sells as well as Diana, he adds, "is the person we're doing next, Elizabeth Taylor."
In Britain, palace watching has become so competitive that every single one of the country's 22 national newspapers has at least one correspondent devoted solely to royals coverage, says John Hannah, an editor for the British news agency Rex Features Ltd. Because they are so private, any information pertaining to the Windsors is highly valued. According to Hannah, Diana alone is worth close to $1 million a year to the agency in sales of stories and photos.
By contrast, there are few reporters assigned to cover only the Monaco royals. "That would come under the heading of the society beat," Hannah explains.
Although each week seems to bring a fresh torrent of Diana stories and at least one TV movie is in the planning stages, Davies believes the fanatic interest in her will inevitably wane.
"To be brutally honest, I do not think they're going to have the same interest in a 50-year-old Diana as they do in a 30-year-old Diana," he says. "It happens to us all."
Schwartz takes an even longer view. Having covered two, going on three generations of royal shenanigans, he sighs, "I imagine in a few years Caroline's three children, and (princes) Harry and William cavorting in nightclubs, getting drunk, falling off ships and impregnating girls. It's going to happen, you know. The royal line continues."