Alive and Armed in L.A. : THE SUN MAIDEN, <i> By Erika Taylor (Atheneum: $19.95; 247 pp.)</i>

Erika Taylor, 26, sets her first novel in an urban milieu very different from those of her contemporaries, Bret Easton Ellis and Jay MacInerny--and what a blessing! Taylor’s heroine, the gawky 20-year-old J. O., can’t afford drugs and never went to college. A recent Midwestern transplant, she inhabits Los Angeles’ less-than-upscale, scrungy Melrose Avenue, thrift-shop world of pale emigres, waifs and wanna-bes. She’s a waitress--a bad one--at the Sun Maiden, an authentic diner: “Los Angeles was filled with fake diners where people put slits in their uniforms and blasted fifties music, places where nobody said ‘hon’ unless they were kidding. At the Sun Maiden everyone said ‘hon’ even if they didn’t like you.”

Like the Sun Maiden, this unprepossessing novel delivers a surprisingly tasty square meal. The author’s exposure to the movie industry probably accounts for “The Sun Maiden’s” speedy three-act plot structure; its coming-of-age story is spiced with entertaining doses of romance, mystery and danger.

J. O. has left her hard-working single mother to seek out her father; all she knows is that he lives in West L.A. She’s a wounded soul seeking nourishment from the outside world but not sure how to get it. She can’t seem to summon up the courage to speak to her father even when, after five months in the city, she reaches him by telephone. “Click. As he hung up I tried to see him sitting there, but all I saw was my mother’s face when I used to ask questions about him.”

J. O.’s roommate, red-haired sexpot Samantha, is a semi-regular on “You’re Busted,” a sitcom cop show. J. O. is awe-stricken by her. “In my heart I hoped if I hung around long enough some of her life might bleed to mine the way red bleeds to white in the laundry. Men loved Samantha, though she usually got bored. I felt pretty retarded being almost twenty-one, the same age as her, and having only slept with Foxtrot my whole life.”

Samantha wants to broaden J. O.’s sexual horizons by setting her up with an artsy screenwriter who has two beautiful birds. “I knew about these birds,” thinks J. O. “Their names would be Agony and Ecstasy, and they’d (crap) on my head.”

While J. O.’s most satisfying L.A. relationship may be with her favorite bank teller, Marilyn, she has another chum, Andy, who drags her into his own family drama. Andy carries a rat named Fear under his jacket and surprises J. O. by being a better Sun Maiden bus boy than she is a waitress. (She can’t seem to get the uniform right, and forgets orders.)

One of “The Sun Maiden’s” subplots involves J. O. and Samantha’s elderly Jewish landlord, Mr. Saul, who claims to be building The Car of the Future in his garage. “The model was bright yellow with narrow diamond-shaped windows, and a Tupperware bowl for its roof. Its hood started out okay, but then gradually thinned to a needle beak point in front so the whole thing looked like the head of some nasty bird. A giant woodpecker.” Mr. Saul is terrified of the loan collectors who are threatening to destroy him and obliterate his creation, which eventually places both tenants in jeopardy.

J. O. finally begins to come out of herself when Rafi, the Sun Maiden’s Israeli manager, almost fires her but instead drives her to the ocean and shows her how to shoot a Smith & Wesson .357 magnum, which she is startled to discover she enjoys. The next time she spills scalding food on herself, Rafi kisses her blazing skin. He starts taking her to his gun club for more shooting dates. J. O. insists on using the .357. “Bam! Rafi’s shots had perfect authority with each one timed a second apart and all six landing dead center. . . . After that, everytime I shot, Rafi followed an instant later which forced me into a rhythm. Him, me, him, it snapped through my body so personally I wanted to close my eyes. We did it that way for a long time.”

Rafi turns out to be a warmly solicitous paternal lover. He fixes her battered Gremlin and tells her she is pretty. “For some reason if people said I was pretty it hurt a little,” J. O. reflects, “but in a strangely satisfying way, like poking a canker sore with your tongue.” But Rafi’s also engaged in some illegal activity that necessitates his abrupt departure from the country. J. O. suddenly finds herself with no lover, no roommate, no car--or apartment either, thanks to Mr. Saul’s loan goons. She does wind up with her landlord’s intact Car of the Future, although it proves unsaleable.

Between Rafi’s attentions, her newfound waitressing competence and the galvanizing power of a revolver, J. O. matures from passive, lonely child to strong woman of action. Although miserable over losing Rafi, she drives Andy up to the Northwest and, packing her gun, boldly takes charge of a potentially explosive family crisis.

While Taylor’s muscular heroine may owe some debt to pistol-packing mamas like the movies’ Thelma and Louise, “The Sun Maiden” nonetheless unveils an exciting young writer who paints a vivid L.A. we haven’t seen before.