Okay, we're going to be frank here, no beating around the bush, no searching for the nice way to put it. Merrill Markoe, former head writer for Late Night with David Letterman, girlfriend of Letterman and mother to two dogs named Stan and Bob, is not a glamorous woman, and she'd probably be the second to tell you so. The woman, quite frankly, is a self-admitted klutz. But that hasn't stopped her from calling her first solo special, debuting this week on Cinemax, Merrill Markoe's Guide to Glamourous Living. Those who can't, teach, right?

"I've always had an obsession with how I can't pull glamour off at any level," says Markoe, 39. "I can't pull off anything without tripping at the wrong spot or finding that I have a big piece of marinara sauce stuck to the corner of my face. I mean, I've never had dinner with anyone where they didn't eventually wipe my face for me or pick bread out of my eyebrows."

Cybill Shepherd she ain't. But she is one of the most talented comedy writers in the biz, playing a large role in creating the slightly skewed tone of Late Night. Hey, she deserves to be in the Comedy Hall of Fame just for thinking up Stupid Pet Tricks. Such success has given her the insouciance and savoir faire for which she's so well known. Take, for example, her experience at the 1986 Emmy Awards. Markoe's belt kept falling off her dress all evening. You could see her clutching it even when she went up to claim her writing award—one of the 10 Emmys she and Letterman have between them, most stowed in the back bathroom of their Malibu home. ("It's not any kind of statement," she says, conducting a tour of the toilet shrine. "We just had shelf space here.")

You'd think that being born in the world's glamour capital, New York, Markoe would have gotten off on the right foot. But Gerry Markoe, a real estate developer, kept his family moving around the country. Merrill was a high school sophomore by the time her father, mother Ronny, a research librarian, and younger brother Glenn, now an archaeologist, finally settled in the San Francisco Bay Area. Earning an M.F.A. in painting from Berkeley in 1974, Markoe taught drawing at the University of Southern California for a year. "I never really fit into academia," she says. "I was this incredible smart-ass who had a lot of humor in her paintings."

Looking for another outlet, Markoe began using her talent in TV scripts and a stand-up routine at Los Angeles comedy clubs. While performing at the Comedy Store in 1977, she met a fellow comic with a mutual sense of observational humor: David Letterman. Recently divorced from his wife of eight years, Michelle Cook, Dave was just looking for laughs, not—how you say?—commitment. But the couple clicked and were soon living together. And Markoe began writing some of Letterman's material. "That was my love thing for him," she says. "I fell in love so I wanted to write jokes for him."

"We had a real good rapport," says Letterman, 41. "She was an excellent source of material for me. I never wrote anything for her though," Dave adds, smiling. "I have a kind of philosophy that has helped me skyrocket to the top—keep the good stuff for yourself."

Markoe continued to put words in Letterman's mouth for a 1978 pilot, Leave It to Dave, which never aired, for his 1980 NBC daytime talkie The David Letterman Show, which lasted 18 weeks, and finally, starting in 1982, for Late Night. While the show benefited from Markoe's contributions (like Elevator Races and the Sponge Suit), being on the payroll put considerable strain on her relationship with Letterman—particularly during the first season, when she was the show's head writer. "It was a totally unmanageable situation," says Letterman. "It was great that I trusted her comedy instincts. On the other hand, I felt like it was a 24-hour-a-day professional relationship. We both grew weary of that. Things are actually better now for everyone because I have no sexual interest in our present head writer, Steve O'Donnell, whatsoever."

After the first season, Markoe stepped down as head scribe and joined the show's writing staff. "It was better to let somebody else fight the minute-to-minute battles," she says. But by 1986 Markoe felt her Late Night tenure was stifling both her creativity and her relationship. "It was very hard for me to leave," she says, "because the show felt like a child that Dave and I had given birth to. But it got to a point where I wanted to do a lot more and couldn't without being in complete conflict with Dave. You get tired of one person always getting the final yes or no, which I'd always let him do."

Moving back to L.A., Markoe wrote sitcom scripts and worked as a feature reporter for KCOP-TV, covering events like the opening of Mickey Rooney's yogurt parlor. Last year she and Harry Shearer co-hosted Cinemax's This Week Indoors, a show that led to Merrill Markoe's Guide to Glamourous Living. Written and directed by its star, the new special features tips on such charm essentials as limousine etiquette and making a proper entrance. Glamourous Living also includes appearances by Letterman, Elayne Boosler, Garry Shandling and 25 of Markoe's own gowns, each one more hideous than the next. "I think they each cost a dollar," she says. "I won't have many occasions to wear them. It would be me in a gown and Dave in a baseball shirt. Dave and I always look like we're going two different places."

Frequently they are. Since Markoe left Late Night, she has spent most of her time in Malibu, while Letterman has held down the fort at their New Canaan, Conn., home. "There's a lot of commuting," she says. At the moment, thanks to the writers' strike, Letterman has been smoking his cigars in the sprawling, single-level West Coast residence. Living apart, allows Letterman, has helped Merrill and the relationship become stronger. "In any walk of life," he says, "the more secure two partners are in their individual pursuits, the better off the union is going to be."

There's no talk of putting the union in writing. "Obviously, marriage isn't really an issue," says Markoe. "If we were going to get married, it would have happened two or three years after we met. At this point it doesn't seem like something we need to do. Actually, I've given up trying to figure out what we're supposed to do. Our relationship defies definition. We're ground-breaking. Call us America's most delightful couple." You name it, you got it.

—By Joanne Kaufman, with Michael Alexander in Los Angeles