From PEOPLE Magazine Click to enlarge
Sitting in a lounge at the Beverly Wilshire Hotel in Los Angeles, Diane Keaton is talking about kissing. Kissing Mel Gibson, to be exact. It was 1984 and they were filming a scene for Mrs. Soffel. "Could he have been more beautiful?" she says. "I was like 39, and he was . . . a baby! I got in the car to go home, and I kept reinventing that kiss. Over and over." She pauses to let the story's swoonworthiness sink in. "That's why the title of my book is Then Again. Because you can go back! And almost reinvent those moments that meant so much."

If you're Diane Keaton, of course, you've had way more replayable moments than most. The Oscar winner (for Annie Hall in 1978) has appeared in more than 40 films, become a style icon and dated "unattainable greats," as she calls them, from Al Pacino to Warren Beatty. Now 65 and single mother to daughter Dexter, 15, and son Duke, 10, she's the rare Hollywood actress who hasn't disappeared from the screen as her youth faded, even playing a love interest-at an un-botoxed 57!-in 2003's Something's Gotta Give. Her new book delves into all that, but it was a sadder reality that inspired it and gave urgency to her interest in preserving memories: Her mother, Dorothy Keaton Hall, whose journal entries make up part of the book, had Alzheimer's and died in '08. Then Again "is not my memoir," Keaton writes, "but ours."

Keaton grew up in L.A. and Orange County, the oldest of four. Her father was a civil engineer, her mother a homemaker whose motto was "my life is this family" but who had unfulfilled dreams: Dorothy wrote, took photos and was crowned Mrs. Los Angeles in 1955. She adored her kids and was "the greatest audience," says her daughter, a C student ("I think I had ADD; instead of listening I'd be lost in the teacher's face") who shone in school plays.

Leaving home for acting school at 19, Keaton got her start in Hair on Broadway-not, she insists, because of her looks. "Nothing was symmetrical, do you know?" she says. "I was friendly looking, no Candy Bergen. The smile, maybe, was all I had." When Hair's director offered her the lead if she'd slim down (at 5'7" she weighed 140 lbs.), she took the criticism to heart, losing 10 lbs. and beginning a five-year battle with bulimia, something she reveals for the first time in her book.

"I don't think it was called bulimia then," she says. "It was just this trick you could do. It's a horrible problem. Ugly and awful." She credits "the talking cure"-she's been in psychoanalysis on and off most of her adult life-for her recovery. One morning she simply "didn't open a half gallon of rocky road ice cream." She began dating Woody Allen pre-recovery; he never knew her secret but did remark that she could really "pack it in."

Keaton lights up when the subject is Woody, still a good friend. "I loved his body," she says (and when it's suggested that she may be in the minority: "He's beautiful! You've got it all wrong"). She quotes his letters in the book: He tells her, "I have decided to let your family make me rich! Rich, do you hear!" Thus was Annie Hall, based on the quirky Keaton/Hall clan, born.

Stardom followed, and with it came high-profile men. "Talent is so damn attractive," Keaton sighs. Some kinds more than others: She dated Steve Jobs a few times in the '80s, but "he'd start saying things about the computer, and I'm going, 'I have no interest.' Do you believe it? So that was the end of that."

She fell hard for Warren Beatty, her costar and director in 1981's Reds. "He was romantic and very kind," she says. Knowing she was afraid of flying, Beatty once surprised her as she boarded a plane to New York, held her hand through the flight, then kissed her and flew back to L.A. But Al Pacino, her costar in the Godfather movies, may well have been the love of her life. "Charming, hilarious, a nonstop talker," she says. "There was an aspect of him that was like a lost orphan, like this kind of crazy idiot savant. And oh, gorgeous! I was mad for him. I worked hard on that one." When he dithered about marriage, she gave him an ultimatum, and it was over. "I went about it not in a perfect way," she says now.

Never married, she thinks she didn't find "a home in the arms of a man," as she puts it, in part because of her mother's cautionary tale. "There was a sacrifice she had to make in not having a career," she says. "I knew marriage was not going to be a friend to me."

Children, she eventually decided, were. At some point "I tried to get pregnant, but not much, you know," she says without elaborating. Instead she adopted Dexter and Duke, with whom she lives in a rented home in Bel Air. Her plate is full these days: A spokeswoman for l'Oreal Cosmetics, she's also designing for Bed, Bath & Beyond and finishing a book on architecture, and she recently shot an ad campaign for Chico's. She has two movies due out in 2012 and says she'll keep acting as long as they'll have her. "I'd like some plastic surgery; slap it on now!" she says with a laugh, pulling the skin back on her cheeks. "No, it's too late. If you start at 65, you'd have a really weird face."

She's not in the market for romance, either. "Maybe I'll buy a companion," she muses. "But dating terrifies me. Can you imagine anything worse? Me going, 'Hi! Mwah!' My kids think the idea's repugnant too. 'Mom, blech!'"

Here's her idea of happiness: "Dinners with Duke and Dexter. We set the table, do the dishes and talk. About their days, the latest nightmare at school-it couldn't be better. I'm sorry, but it's better than any of your fantasies about love . . . it is love. That's the best thing." So far from the life her mother led, and yet not so far at all.