The amazing thing about Christie Brinkley’s “Timeless Beauty: Over 100 Tips, Secrets & Shortcuts to Looking & Feeling Great” isn’t the cover photo but the asterisk beside her name, followed by the phrase, “who happens to be 61 years old.”

So much for Gloria Steinem’s “This is what 50 looks like.” Brinkley — the perennial Uptown Girl and mother of three — turns 62 in February. Clearly, she’ll have to update her book jacket.

“Who knows?” she tells The Post, giggling. “Maybe I’ll write another in 30 years, when I’m 90.”

Her math may be shaky, but her figure isn’t. Last year she posed for a People magazine cover in a slinky one-piece, surprising even herself. She laughs, recalling an old magazine cover of herself with the headline, “This is my last bathing suit cover!”

“I think I was 35, and aware of a little pooch on my stomach,” she says. “We’re so hard on ourselves! I think the way you look is tied into how you feel. The kind of true beauty I hope my readers are looking for is a combination of healthy living and good deeds.”

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Out Tuesday, “Timeless Beauty” stresses the virtues of smiling more, exercising regularly and avoiding meat, all of which Brinkley believes in. A vegetarian most of her life — a decision she made at 14, after reading about slaughterhouses — Brinkley veers toward veganism, with the occasional lapse. “When in Roma, do what you don’t do at home-a,” she singsongs. “Have some mozzarella!”

Along with recipes for zucchini lasagna and other dishes are tips on makeup, wardrobe and hair — and how to find a good dermatologist. While Brinkley calls liposuction “kinda scary,” she believes lasers and fillers, when administered properly, can work wonders. She owns up to having “several different treatments” herself, including a disastrous bout of Botox several summers ago.

“It made me look like I was punched in the eye,” she says. “I couldn’t move my forehead. I had to wear hats!” Then again, she adds, Botox worked wonders with smoothing out the wrinkles on her neck."

Her late mother, Marjorie, an intrepid traveler, hostess and mother of two, had a streamlined approach to beauty. “She had the most radiant smile in the world, and a makeup bag the size of a pencil case!” says Brinkley, who grew up admiring Grace Kelly’s “simple, classic look” and Lauren Bacall’s “alluring” hair. Asked whom she finds most beautiful today, she names Jennifer Lawrence — “because she’s so sparkly and has so much personality, she just radiates!” — and Emma Stone (“When she enters a room, you want to see what she’s wearing”).

It wasn’t until she was 57 and kicking up her heels in Broadway’s “Chicago” that Brinkley felt the pull of age and gravity. “I sustained so many injuries,” she says. “Doctors told me I needed a double-hip replacement and rotator-cuff surgery.”

Instead, she opted for physical therapy, and was thrilled with the results. “I saw my body get back into shape again,” she marvels. “I had the right to bare arms again!”

A head full of hair extensions doesn’t hurt, either. Christie, who has her own line of them, says she’s wearing two in her book cover photo.

“It’s easier to go out and change the world on a good hair day,” she says. “So let’s get you out of the door so you can focus on the things that really matter.”

Click here to read more of Brinkley's beauty tips in the New York Post.