Can Sarah Jessica Parker really embody Kate Reddy?

Sarah Jessica Parker stars as Kate Reddy in “I Don't Know How She Does It.” (Brendon Thorne/Getty Images)

The movie version of the British book will open Friday, with Parker in the role of a stretched-too-thin working mother. “Too thin” is literally true to some fans since one of the biggest complaints among readers and potential viewers of “I Don’t Know” is that Parker is too thin, and stylish, to reflect the frazzled main character.

The author herself alluded to the Hollywood-ization of her heroine, even as she promoted the choice in a column she wrote for The Telegraph Friday:

“Well, the woman on the screen is not my self-lacerating heroine, but SJP is utterly convincing as [a] financial whizz and a woman stretched like an elastic band as she tries to honour her love for her family and her dedication to her work,” Pearson wrote.

Hollywood was in a tough bind with the screen adaptation of this book. Like another beloved modern British literary character before her, Bridget Jones, the appeal comes in her every-woman-ness. Hollywood specializes in perfection, not ordinary, so casting these sorts is always a problem. Renee Zellweger had to agree to down several milkshakes before the audience embraced her as frumpily believable in “Bridget Jones’s Diary” in 2001.

The disconnect between Parker and Reddy is not so much weight or looks, really. It’s more rooted in identity and identification. Parker became an icon for many women when she starred as sexy New York writer Carrie Bradshaw in HBO’s “Sex and the City.” The show, and the two movies it spawned, was an escapist fantasy for so many because Parker’s character lived a life of extreme independence, frivolousness and profound self-centeredness — qualities that if an ordinary woman ever possessed them, were surely excised once children came into their lives.

The literary character of Kate Reddy found a fan base among mothers for the exact opposite reason. She reflected the unglamorous, overwhelmed experience. Of course, the narrative is not anything close to an honest depiction of modern parenting, given the character’s lofty salary among other conveniently unrealistic elements. The movie, like the book, is faux, or froth, reality.

Still, the theme is that Reddy can’t keep up with the mundane demands of work, husband and kids. That’s no fantasy. The only thing pretty about it is that it’s pretty universal.

Come Friday, with Kate Reddy’s makeover, that experience will seem even glossier than the book’s version.What Hollywood’s betting is that it’s not a deal-breaker for the movie. After all, the desire to see one’s reflection gussied up, especially for those of us who feel rundown on a regular basis, is pretty universal too.