This novel is not easy to classify. Both endearingly fluffy and somewhat "dark" and kinky, it can't quite make up its mind what it wants to be. Perhaps this is not surprising, since the heroine, Isobel, has the same ambivalence about her own life --- even her own personality.

At 52, Isobel is a prize-winning British literary novelist with a lovely house in Kent and a chronically ill, financially dependent husband. Her dilemma: The latest book --- all of which have Austen-esque titles like The Dream and the Doing --- is going to earn a paltry advance from her publisher, not enough to maintain her house, housekeeper, and husband (who is fond of helping himself to ten-pound notes and strolling down to the local pub). Her agent, "boyishly handsome," sexually ambiguous, Armani-clad Troy, breaks the news to her over lunch at a hot new restaurant. It's the market, he explains. She's too good for it. All they want is drivel.

On the spot --- literally at the table --- Isobel, convinced that "any fool" can write a best-selling novel, spins a plot so trashy, so sexy, so compelling that even the waiter listens in. Then she sits down and writes the thing. (And just as you're thinking that ZELDA'S CUT is, itself, one of those distinctly unliterary productions, Philippa Gregory comes up with a nice touch: When Isobel turns in the manuscript, Troy calls her to say there's a problem with it. "It's these semicolons... Nobody in popular fiction uses semicolons. They wouldn't know what to do with them..." Definitely Austen-esque.)

But wait. If the heroine is named Isobel, who's Zelda? She is the blonde, gorgeous, over-the-top creature with a Swiss bank account and lavish wardrobe purchased on a Harrods shopping spree worthy of Judith Krantz whom Troy and Isobel invent to pose as the true author of Devil's Disciple. Soon, Isobel is heavily into a double life. One week she is in London making TV appearances as Zelda (in a funny scene, Isobel unconsciously breaks out of her Zelda self and uses words like tautology and archetype; "Tell her to shut her mouth up and simper," yells the outraged talk-show host during a commercial break). The next week, she's zipping back to Kent and Philip (who has graduated from pub crawling to laying lavish plans for an indoor swimming pool). Most important, her relationship with Troy takes an unusual turn --- a lot more sexually bizarre than I'd bargained for. I won't give away the plot twists, including a surprise ending; suffice it to say that they involve gender-bending, unwise investments, and obsessional behavior of all sorts.

I've read some of Philippa Gregory's previous fiction --- two well-crafted and absorbing if not quite grade-A historical novels, also with more than a whiff of unconventional sex (maybe that is one of her trademarks). These earlier novels are anchored and burnished by her fresh re-imagining of a historical period: the Civil War of 17th-century England as seen through the eyes of a garden designer/horticulturist to the royal family. Here, confined to a contemporary landscape, her work is more one-dimensional.

ZELDA'S CUT is a diverting tale with flashes of wit, nicely managed tension, and a thoroughly likable protagonist. But, although Gregory wants to bring Isobel's two halves together --- write a novel smart enough to attract a reader with literary tastes and sensational enough to sell like John Grisham --- she doesn't altogether succeed. I'd call the book a prime-time miniseries rather than a "Masterpiece Theatre" production.