If Robert Ludlum ever had a notion to write something like "When Harry Met Sally," he might end up with something like "Just Friends," the novel by Londoner Robyn Sisman. Like so many of Ludlum's books, "Just Friends" is far more a pleasure to read than to complete.

From the opening gun, Sisman delivers pleasant prose, clever repartee, and insight into the differences between men and women, albeit firmly from a modern woman's point of view. But less than a third of the way into the book, I hadn't so much figured out the ending as I'd begun to fear it: Sisman wouldn't cap the book's refreshing sass with a tired finish, would she?

As the book opens, Freya Penrose is changing into clingy new clothes in the office ladies' room at the end of a tough week: Michael, her live-in lover, has asked her out for a special night, so they "can talk." She thinks he might be the one, and she thinks tonight might be the night.

That Sisman can achieve any suspense at all is impressive, since her title begs the assumption that the couple in the opening tableau isn't going to get engaged. They don't, even though it turns out that they're not the principal pairing.

That distinction is reserved for Freya and Jack Madison, a trust- funded novelist with whom she's been friends for years. He's cute and all, but he's never made marriage grade because he has always gone for 22-year-olds whose bods are more developed than their brains.

Freya's reaction to Michael's rejection is to head for Jack's. She hasn't seen him in months, roughly the time since she moved in with Michael, but not only does she have nowhere else to go, but it's the first Friday of the month, which means Jack is hosting his poker game. She knows she'll find thick smoke, too much liquor, and the subtle juice that flows at the poker table. Better yet, there'll be no women; she has always been more comfortable in the company of men.

"There was none of that sly innuendo you got with women, no prying questions, no edgy competitiveness; just sports, jokes, news stories, media gossip, sex." Freya's cards start out hot, but as she plays, she drinks, and by the time she has passed out on the couch, she's the big loser for the second time in a night.

Jack doesn't learn of the breakup until the next morning, when he calls Michael to tell him Freya's still sleeping it off, but OK: "What a mystery women were. He'd known Freya for over 10 years, yet she wouldn't tell him she'd split up with her boyfriend; whereas Michael, whom he'd met about twice and didn't even like, had told him right away." Jack, and the rest of us, learn the true nature of Michael's friendship when Jack protests that Freya is ill and needs somewhere to go: "You're her friend," Michael growls, "you take care of her."

What an awful idea, Jack quickly concludes, but after an attack of conscience, he does indeed ask her to move in, for "two weeks absolute max," while she gets straightened away.

Within days, of course, they're at each other's throats. At breakfast on Day 3, for example, when Freya prattles on about the latest tabloid gossip, Jack gains an inch when he sniffs: "I prefer not to clutter my mind with trivia." But he loses a mile when he continues, "Now might I trouble you for the sports section?"

The women in Sisman's world are not perfect, but their foibles come with sympathy, such as when Freya looks inward over the breakup: "Michael was one of the few single men in New York actively seeking a long-term partner - OK, wife - yet he had discounted her as a possibility. Why? Was she too tall? Too thin? Were her breasts too small?" Later, her doubts cut deeper: "Could it be the fault lay with her, that she was unworthy of love?"

But Freya is brave, and she comes through her introspection whole, even after the unkindest cut, which comes during her stepsister's wedding back home in Britain. Jack accompanies her, though only as her beard, to allow Freya to "prove" she's worthy of love. The jaunt allows Sisman, meanwhile, to riff on Brits.

Jack's vocation as a writer allows Sisman to tramp more ground she apparently knows well, the publishing industry. Jack has been stifled in his writing for some time, for example, but that doesn't stop a soulless agent from chatting him up with lines such as, "it's totally irrelevant whether the book is good."

It will come as no surprise by now that the soulless one is a guy. And Jack's current agent, who has stood by him through the tough times, is, of course, a woman. Even so, it's not the male bashing that ultimately undoes "Just Friends"; she's tougher on men, but truth is a defense.

It's difficult to specify just why the end is disappointing without revealing too much. And perhaps other readers won't react the same way. But to me, for all the book's varied brightness, the plot of "Just Friends" is just all right.