It’s easy to understand why Campbell Scott leapt at the chance to star as the breezily cynical, somewhat pathetic womanizer called “Roger Dodger.” Writer-director Dylan Kidd reportedly passed the script along to Scott when he spied the actor in a New York restaurant, and Scott, it’s said, accepted it gingerly, hardly expecting to wind up co-producing it as well as starring. But when he got around to reading the screenplay, he must have found it irresistible: Roger’s not only on screen constantly–he’s a driven, articulate, desperate, queasily attractive yet peculiarly sad figure. What more could a young actor want? It’s a virtuoso part, the sort that comes around once in a blue moon (just think of what “Swimming With Sharks” did for Kevin Spacey). And it’s perfect for Scott’s deceptively bland, boyish good looks and slightly serpentine manner, besides putting his ability to spit out rapid-fire dialogue to good use.

Happily, his enthusiastic reaction to Kidd’s work proves to have been sound. “Roger” is a slight piece–one of those talkathons that’s more monologue than anything else, the kind of gabfest that might actually be more at home on the stage. (As director, Kidd’s response is to keep everything jittery by using a hand-held camera throughout, thereby increasing the level of nervous tension with a minimum of fuss.) But though hardly complex, the character of Roger is one of those rich thin characters who may not change or grow over the story’s brief span but is sufficiently colorful and compelling easily to hold one’s attention over a two-hour period, though he’d be exhausting and unpleasant to encounter in real life. Watching him not only spew his obsessive, self-destructive bilge but pass it on to his virginal nephew Nick (Jesse Eisenberg, in a closely observed turn that puts his performance in “The Emperor’s Club” in the shade) proves morbidly fascinating–rather like peering at an odd organism writhing about on a specimen dish under a laboratory microscope. And this one talks a blue streak, too.

Like most films of this ilk, “Roger Dodger” is a very simple affair. We meet the title character, a fast-talking advertising man, having an after-hours drink with his boss Joyce (Isabella Rossellini) and a couple of colleagues. He rants freely about the differences between the sexes, earning plenty of laughs and groans in the process, and afterward shows up at Joyce’s apartment for some sack time. It’s clear, however, that she’s breaking off the affair they’ve been having, and equally obvious he’s not taking it well. It’s at this point that Roger’s nephew shows up, supposedly in town from Ohio to scope out the Columbia campus, and before long the duo has snuck into a back table at a bar, where the older man tries to instruct the kid in the techniques of snaring babes. Before long they’ve collared a pair of initially incredulous young women (Elizabeth Berkley and Jennifer Beals) whom Roger urges Nick to try a line of lies on. Andrea and Sophie, as they’re called, are hardly taken in, but they develop a bemused affection for Nick (none for Roger, though, whom they peg as a sleazebag); but when the youngster is unable to “close the deal,” from his uncle’s point of view, they move on to a party at Joyce’s place, even though Roger had specifically been uninvited from it. He tries to set Nick up with a drunken co-worker, but when that doesn’t work out either (and Roger is ejected), they wind up in desperation at a brothel. A couple of none too surprising revelations are followed by an amusing postscript back in Nick’s Ohio hometown.

“Roger Dodger” is an uneven affair, which tends to lose steam as it goes along, and except for the Midwest sequence, featuring some impossibly geeky high school kids, the later episodes don’t match the earlier ones. Kidd’s apparent desire to equate the shallowness of Roger’s character with the soullessness of his job doesn’t quite come off, either. But the sharpness of much of Kidd’s dialogue, along with Scott’s skillful seediness and Eisenberg’s knowing portrait of adolescent lust, make even the last half hour of the picture palatable. (The contributions of Rossellini, Berkley and Beals are fine, too.) Outside the theatre Roger might be intolerable company, but inside it he’s well worth spending some time with.