Nobody sold newspapers like Princess Diana, and now Tina Brown is hoping that juicy memories of the People's Princess will do the same for her first book.

"I'm very well-sourced in the book in the sense that I did 225 new interviews, and many of those were really insiders in the royal circle," Brown said over a cup of tea on a recent afternoon at the Ritz-Carlton Georgetown. Still, she was surprised by the enthusiastic response from critics.

Diana was a natural subject for Brown's first book because coverage of the princess helped define Brown's journalistic career, and she knew many people in Diana's world. Brown said she was particularly taken with Diana as a subject.

"When you think of the great, iconic stories that people seem to have kind of bottomless interest in, you think about Marilyn (Monroe) and John F. Kennedy and Diana," Brown said. "I think Diana has left an enormous footprint."

The book has already jumped onto lists of best sellers, including Amazon.com. "Clearly, early sales have been quite strong," said Alison Rich, a spokeswoman for Brown's publisher, Doubleday. Rich said the book is in its fifth printing — up to 245,000 copies.

Now 54, Brown still wears a haircut similar to Diana — short and blond — and an understated black dress. She's been on a media blitz for the better part of a week, generating that all-important buzz she used to sell magazines.

Her editor says the time was right for the Diana book. "It was her 10th anniversary, and Tina was ready to write the book," said editor Phyllis Grann. "I just thought it was the ideal match of subject and author."

Brown had been working on the book since she started covering Diana as the 25-year-old editor of London's Tatler magazine. As Diana's star rose, so did Brown's. From Tatler to Vanity Fair to The New Yorker, Brown explained the royals to America — and sold magazines. She scored big with a 1985 cover story in Vanity Fair, "The Mouse the Roared," which broke the story of Charles and Diana's marital breakdown.

The "Chronicles" details Diana's wounds from her childhood with her parent's divorce and her mother leaving when she was only 6. It dredges up a rumor over Diana's virginity before her engagement to Charles, once thought debunked. But Brown assures that she has confirmed that Diana did indeed visit Charles twice in the middle of the night for what's thought to be a secret love tryst on the royal train. She says it wasn't Camilla Parker Bowles on the "love train," as some had thought.

"I basically found the source of the story in the first place, and I discovered that a policeman who had been at the train sighting had faxed through the number plate of the car that was going to meet Charles," Brown said. The car belonged to Frances Shand Kydd, Diana's mother. "So either we're to assume that Diana's mother was having an affair with Charles, or it was Diana on the royal train."

Both 19-year-old Diana and the palace insisted it wasn't her.

"It seems clear now that Diana, for reasons of panicked self-protection, colluded with the Palace machine to protect the anachronistic facade of virginity," Brown wrote. "In a sense, the Love Train incident was the moment she first became a Royal."

Brown said she tried to balance the joys and pain of Diana's life. Fast-forward to perhaps the height of Diana's world fame as a royal. Brown was proud to nab an interview with actor John Travolta about his memories of dancing with Princess Diana in 1985 at the Reagan White House. It made for one of her favorite chapters.

"As soon as we get out there, the whole place clears for our encounter," Travolta told Brown. "And I look her in the eyes and reassure her with my eyes to say, 'We're OK.' We probably only dance 10 minutes, but it feels like 20."

Brown said it was a magical night because the "fairy story" of Diana became a Hollywood story. "One of the happiest scenes ... is that night when the world was at her feet and she felt good about it all," Brown said.

The constant problem: Diana was always outshining her husband, Brown writes.

Among Diana's strongest legacies, Brown said, was changing the monarchy by giving it a more a modern, compassionate and accessible face. The birthday concert Prince William and Prince Harry are throwing for their mother this July 1 is a good example, Brown said.

Diana was also the forerunner for celebrity activists who take on serious humanitarian issues, such as Bono and Angelina Jolie, Brown said. "With each cycle of the era, everything she did had this very generational echo," Brown said. "This was a very different kind of royalty than we'd seen."

Brown met Diana for a long lunch in New York in the summer of 1997, just before her death. The princess had become a confident and "totally evolved sort of global superstar," Brown said. But that was before a downward spiral leading to her death. The popular princess suffered from lapses into terrible insecurity and no self worth. Brown said she later realized Diana had just been rejected by her last true love, a Pakistani doctor named Hasnat Khan, and she was irritated that Charles had thrown a 50th birthday celebration for Camilla.

"It was a throwback to the worst moments in her life, where she felt so abandoned," Brown said. "So she went off with Dodi (Fayed) in a sense just for the protection. That was the irony." Diana's critical mistake, Brown said, was giving up royal security. If she hadn't, she would never have been driven with Fayed by a drunken chauffeur through that Paris tunnel.

Brown would like to write another book after two short-lived media ventures — the glossy Talk magazine and a short run with her own CNBC talk show. For now, though, she offers the "Chronicles" as a social history of the monarchy.

"There were no villains in this story," Brown said. "There were human beings, struggling under pressure, put into a difficult box where they tried to do their best, but were often thwarted by passion and love and the press and the tradition."