Jennifer Weiner's novels featuring "plus-size" women seem to be worth their weight in gold.

Her first three books, "Good in Bed," "Little Earthquakes" and "In Her Shoes," have sold nearly 5 million copies in 33 countries.

The film version of "In Her Shoes," starring Cameron Diaz, Toni Collette and Shirley MacLaine, opens Oct. 7. Universal is working on a script for "Little Earthquakes."

And Weiner's fourth novel, "Goodnight Nobody," is in bookstores. The story is about Kate Klein, a woman whose adjustment to suburban life can be called difficult at best.

Kate has three kids, she's not getting along with her husband, she doesn't seem to fit in with the other mothers in the neighborhood, and then, one day, one of the mothers is found dead.

It's the first time Weiner, 35, has used a mystery to drive her plot.

"I wanted to write about motherhood and about the suburbs, and it was a question of, what is this woman's journey going to be, and how do I get it going? And there are few things that start a story better than a body on a kitchen floor."

Few real women are solving murder mysteries, but much of Weiner's popularity is based on her realistic characters. "My characters are all kind of versions of me, but much funnier," she says.

" 'Good in Bed' (which she wrote after she broke up with a boyfriend) was the most autobiographical. 'Little Earthquakes' had elements of me in terms of pregnancy and newborn motherhood."

"This one's a little different though. I don't have three kids. I don't live in the suburbs. I'm not dealing with issues in my marriage that Kate deals with in hers."

Weiner and her husband, Adam, a lawyer, live in Philadelphia with their 2-year-old daughter, Lucy.

Besides relationships, the common denominator in all Weiner's books is her plus-size characters.

"It's important to me, because in so many books, including the ones I read when I was growing up, the big girl was the punch line, or she would get Prince Charming and everything that came with it only after she lost a lot of weight.

"I wanted to talk about characters who were bigger than your average starlet. My God, the salad I ate for lunch is bigger than the average starlet these days."

Weiner talks openly about being "a big girl," but she won't reveal the size of the designer gown she wore to the premiere of "In Her Shoes" this month in Toronto.

She says the designer, Marina Rinaldi, creates for sizes 14 to 24. "I think that'll tell you something."

Being comfortable with her size and talking about it is an evolving process, she says.

"I don't have bulletproof self-esteem. I certainly have days when it's like, 'Where's that burqa?' "

Weiner says she writes about a world "where happiness and happily-ever-after doesn't begin at size 0 and end at size 6, and where there are possibilities for love and happiness and professional success and great friends and a wonderful life even if you don't look like one of those girls in the magazines."

So how does she feel about her publisher putting the very skinny actress Diaz on the cover of the motion picture tie-in paperback of "In Her Shoes"?

"You need the sizzle to sell the steak," Weiner says. "Maybe people will pick up this book and go see the movie."

And, she says she is happy with the movie, even though Collette, who plays Rose, is nowhere near plus-size.

"So much of Rose's problem is in her head as opposed to her actual physical self. It's her history of always having been the bigger sister, not as pretty as the younger one. She internalized that so much that even if she was a size 0, she's still feels like the fat girl."

Weiner hopes the movie's success will help her have more control over actresses chosen for any projects. "It's important for there to be women in the public eye who are bigger than these little twig movie stars."