(CNN) -- Kitty Kelley, author of the controversial biography "Oprah," has a motto over her desk that speaks to her philosophy about her profession as a celebrity biographer: "Tell the truth, but ride a fast horse."
The first three words of that statement capsulate the work that authors like Ian Halperin, Christopher Andersen and Kelley say they strive to do, whether those tomes they pen are authorized by their famous subjects or not.
That last part? Suffice to say, their truth-telling doesn't always go over so well.
Perhaps if they didn't focus their efforts on such high-profile people -- Jackie Kennedy Onassis, Princess Diana, the Bush family, the Clintons, the Reagans, Britain's royal family, the Jolie-Pitts and Madonna have all been placed under one of these authors' microscopes -- they wouldn't find themselves mired in controversy. But Kelley, like Halperin and Andersen, doesn't care to lend her attention to anyone but the rich, famous and powerful.
"I recognize that my books, which put cherished icons under scrutiny, are uncomfortable for some people. Some people would prefer the fairy tale, and I understand that," Kelley said.
"For years," she added, "I've been introduced as an unauthorized biographer, and it used to make me squirm a little bit because the word sounds so nefarious, kind of like breaking and entering. But that's what biography is. It does break and enter a life. I'm much more comfortable with the word now. I own it, I stand up to it, and I don't want to live in a world where all my information is authorized."
As Andersen put it via e-mail, "If you want an inflated publicity release, read an authorized biography. If you want the truth, read an unauthorized biography by a reputable journalist who has a history of getting the facts straight."
Andersen, who has had 13 biographies on the New York Times best-seller list, has stuck with this line of work because he thinks "the public has the right to know everything I can legitimately find out about my subjects. It's not my business to decide what it is the reader should or should not know. I'd be cheating them otherwise. I'm a journalist, not a censor."
Kelley, who started her career as a researcher for the Washington Post editorial page, also refers to herself as a journalist, one who can consistently produce a dizzying number of sources for any given biography as proof of thorough research. For her work on Oprah Winfrey, it was more than 850 interviews.
"If you're writing a book like I'm writing, you owe it to your subject to do that, because you have to do a full-life story, and that means you want to get as many people as possible whose lives have intersected with Oprah's," Kelley said.
The trick is not to be limited by the people who won't talk, because there's always someone who will, Andersen said. To get the job done right, persistence is of the essence.
While writing about Princess Diana, "There was a concerted effort on the part of the royal family to stonewall me after [her] death, but I managed to find hundreds of people who were eager to tell what they knew," Andersen recalled. "There are always a surprising number of people out there who are willing to tell what they know but just haven't been asked -- or not asked in the right way. Incidentally, it sometimes takes six months or so to persuade a source to cooperate. ... It helps to be relentless."
Yet just because a source will spill the details doesn't mean they want anyone to know that they did, and those anonymous wells of private information can make an author's research appear flimsy under the scrutiny of public perception. But, the authors said, granting anonymity to sources is often necessary when writing about high-profile people.
"Most of my sources are on the record. I'd say about 80 percent, but you definitely need some anonymous sources, because these people are afraid to burn bridges," said Halperin, who wrote "Unmasked: The Final Years of Michael Jackson."
At the same time, an author has to be wary of those who are interested in revealing "secrets" because they'd like to see that celebrity -- or the celebrity biographer -- fall flat on their face.
"There's no shortage of people trying to set me up, who want to see me get egg on my face," Halperin said. "What you need is Woodward and Bernstein[-style reporting], mainly for their technique. From a reporting method of extreme corroboration, you need at least three credible sources with matching stories. That's how you get it done. If they have an outlandish story, it'll never make it to print."
And yet suspicious critics persist with each printing of an unauthorized tell-all. Halperin said he had many people calling for the end of his career once "Unmasked" was published because he claimed that Jackson was gay. Kelley's books, on the other hand, have been referred to as "kitty litter," and many news organizations declined to speak with her about her biography of Winfrey.
There's a reason doubts plague tell-alls, said Chicago Tribune literary editor Elizabeth Taylor, and it's not just because it may be unauthorized. Authorized biographies have their problems, too.
"Just because a biography is authorized doesn't mean it's true. It's very, very possible to do an incredibly accurate book without the main subjects ever speaking with the author," Taylor said. "I really think it gets back to the question of evidence and sourcing; just because somebody says something's true doesn't mean it is."
With many of these books, Taylor added, "you can tell from the first paragraph that they're playing fast and loose with sources; you can tell in the way they're written. Because, in good nonfiction, there are great attributions, and the footnotes are a work of art.
"I'm not saying footnotes will make a book, but I think you can really judge the evidence in the footnotes of a lot of these books," she said, pointing to New Yorker editor David Remnick's book "The Bridge: The Life and Rise of Barack Obama" as an example of solid evidence.
"It was so well-sourced, with beautiful writing. The richness of detail was extraordinary," she said. "I think biographies can be both page-turners and truthful."
It is true that "with an unauthorized book, a lot of them are crap, quite frankly," said Peter McGuigan, founding literary agent of Foundry Literary and Media. "They're thrown together and published by no-name publishers who see a hole in the market."
But the big presses aren't interested in risking a potential lawsuit, he said, and the author's documentation and evidence for their claims are vetted thoroughly.
"Every publisher's going to do a legal read," McGuigan explained. "They will guide you on what you can't say, how to say things and when to take something out."
McGuigan -- who has sold two unauthorized biographies to large publishing houses, one on Van Halen and the other on the Police -- said a legal agreement is drafted in which they "warrant and indemnify each other on everything that we do. Meaning that at the end of the day, the writer is accountable for every thing that he writes, but if he's arbitrarily attacked, the publisher will protect them.
"Similarly, the author's not responsible if the publisher tries to change something in the book and gets sued for it."
As complicated and volatile as these books can be, if the author has a reputation as a well-sourced journalist and if the subject is titillating enough, there's little reason for a publishing house to pass on an unauthorized biography, McGuigan said.
"Celebrity books are very appealing to publishers because they come with half the ingredients already there; it makes their job of finding something they can sell in great numbers up front a little bit easier," he said.
And the debate over whether a biography holds any weight isn't always a negative thing; in fact, it can be part of the reason why these books are so lucrative.
"There's a time when you bury the word 'unauthorized' because you're trying to fool the public, but then there's a time when the biggest word on the cover is going to be 'unauthorized,' because you want people to say, 'ah ha, they're going to talk about the pills and the sex and the beatings' and whatever it is people want to get out of these stories," McGuigan said.
"Controversy gets people paying attention," he added, "and once people are paying attention, you're halfway to the cash register."
But Kelley argues that in the end, "the key to success is that the facts are so well documented and stand up at the end of the day. A book wouldn't sell a million copies if readers didn't take away some kind of understanding, illumination or even some kind of entertainment."
There will always be critics, she added, because the books are controversial, but she stands behind what she writes and tries to brush off the allegations of inaccuracy.
"As a friend said, tall trees gather strong wind. If you stand up and you're not part of the short shrubs on the ground and you stick out your neck and write about cherished figures in the establishment," Kelley said, "then you're going to catch some heat."