BY DESIGN : Beauty’s Ugly Side : Drugs. Betrayals. Failures. Two new books expose modeling’s blemishes.

Judging by the public’s fascination with models, any book that has them as a subject has a guaranteed audience.

Throw in sex, back-stabbing, drugs, heart-wrenching failures and dizzying successes and the result is “Model: The Ugly Business of Beautiful Women” (William Morrow), Michael Gross’ excruciatingly detailed look at the history of modeling.

But try engaging those same models, along with plastic surgeons and bodybuilders, in a philosophical discourse on beauty’s privileges and power, and you have “The Beauty Trip” (Pocket Books), novelist Ken Siman’s insightful work.

By some literary coincidence, both authors turned up in Los Angeles--home to plenty of beautiful people--the same day a few weeks ago to flog their recently published books and discuss that most arbitrary of human attributes: beauty.

“Whenever I would bring up the subject, people would say ‘beauty shines through’ or ‘beauty is in the eye of the beholder,’ ” says Siman in the lobby of his hotel, the fashionable Chateau Marmount in West Hollywood. “I thought these were cliches that weren’t heartfelt. They were said to avoid the conversation.”

Siman’s interest in appearances came to the reading public’s attention in his bestseller “Pizza Face,” a story about an acne-scarred youth he calls “completely autobiographical.” Having up-close and personal experiences with the beautiful people caused him another round of personal examination.

“These are really extraordinary-looking people,” he said, “and once you acknowledge that they are much more extraordinary looking than you, at least in my case, your vanity is bound to be bruised.”

Still, Siman carried on. “What I did was spend three years with people who possessed beauty or who were trying to create it. I tried to have an extended conversation.”

Neither Siman nor Gross would be accused of being beautiful. And they’re polar opposites. Siman is well over six feet tall, gangly and shy. Gross, who held court in “what appeared to have once been a bridal department fitting room” after a book signing at Saks Fifth Avenue in Beverly Hills, is well under six feet tall, hyper and supremely self-confident. It didn’t hurt that his book had just made the New York Times bestseller list.

Nevertheless, Gross has been criticized for heaping too much minutia into his 500-plus-page book. For every tale of a drug-induced suicide or description of a sadistic photographer, there is a chapter on the intricacies of the business of model agencies and a chapter on a model who represented her decade.

“Part of the reason I felt it was important to go all the way back was to talk to women who had perspective,” he said. “What’s that Neil Young line? ‘I’ve seen the needle and the damage done.’ You don’t see that at first.”

One of the most poignant stories Gross said he heard was from model Dorian Leigh, older sister of model Suzy Parker, who told him: “I couldn’t run an agency anymore. I could no longer look one of these girls in the face and lie to them and tell them they would have a wonderful life.”

“This woman was the super-model of her age (the ‘40s and ‘50s). She had the most glamorous life imaginable. She was the girl who had everything. She was a jet-setter before there were jets. And she sat at her dining-room table and cried over the waste and the loss.”

According to Gross, Leigh now lives in Southern California, financially close to the edge. All trappings of her once glamorous life have disappeared.

Siman elicits an equally poignant story from the well-known model Carmen Dell’Orefice, who at 62 is still working. She was abandoned by several husbands and recently her financial manager left her too--taking her money with him.

“It’s so easy to lose your sense of reality in this world,” Gross said. “It’s a world where reality has no value. The only value is illusion.”

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While illusion plays a strong role in both books, the only names to turn up in both are models Cindy Crawford and Dell’Orefice, agent Eileen Ford and photographer Arthur Elgort.

In Gross’ book, they are indexed by their business moves, such as “background,” “retirement,” “declining career of” and “nude posing.”

Siman gives each person a chapter. Although he never spoke directly to Crawford, and Eileen Ford gave him short shrift, Dell’Orefice and Elgort were graciously accommodating.

“The Beauty Trip” also features a few quirky sources, such as Sy Sperling (Hair Club for Men) and Dorothy McGuire of the McGuire Sisters. The result is an offbeat collection of memories, rationalizations, evasions and the author’s own thoughts on the topic.

“If it is true that beauty shines through,” Siman says, “then we would be able to spot evil on sight. We could spot our best friends on sight. The only way you can only tell what someone’s like, I’m convinced after writing this, is through their deeds and over time.”

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Of course, evil deeds are what most of us want to read about. Those deeds--done by the beautiful and those who would exploit them--are tallied and scrutinized by Gross in “Model,” just as one might suspect from an author who worked for the New York Times and New York magazine.

“The Times taught me how to do my job,” Gross says, “and New York magazine gave me the freedom to be myself. They both had their value.”

His zealousness for the microscopic picture paid off. He found that former President Gerald Ford once owned a piece of Harry Conover’s modeling agency.

Gross reportedly has made enemies in the industry (he says he was barred from the Todd Oldham show at the request of Naomi Campbell, who disliked the book).

“Johnny Casablancas, in an interview in USA Today, announced he was going to seek an injunction against the publication of this book,” Gross says. “He called it ‘unfortunately accurate.’ I don’t think I could get a better review.”

Gross says many people in the modeling business--”including people who have publicly condemned me”--have told him privately, “You’ve done a good job. It had to be done.”’

Too-close scrutiny of models and the business is not healthy, Siman says.

“The thing about fashion-world beauty, for all its faults, is (that) it allows us to stare at amazingly beautiful people without having to worry about being beat up or being served restraining orders.”