Vacuum Cleaner for Various Voices. INTERVIEW: AUTHOR VERONICA GENG

WRITER Veronica Geng wants people to think she's normal, even if her short, humorous pieces aren't - so she put explainers after each one in a recently published collection. The explainer tells how she got the idea, who she bounced her ideas off of, and generally demystifies the sometimes obscure world of satire. ``It was a way of of saying `look ... I'm not this weirdo, baffling, difficult, arcane, kooky nut who gets these crazy ideas,''' says Ms. Geng, eating salmon salad in her Upper East Side apartment. ``I'm just like a normal person, I talk to my friends on the phone. I read the newspaper. I go to a movie. I put a few things together - and it's ... this.''

``This'' is a type of writing called ``casuals'' which humorist S.J. Perelman made popular in The New Yorker magazine in the '30s. The style has continued, adopted and adapted by new writers ever since. Casuals join disparate subjects in a humorous way, often developing a whole story out of a quotation gleaned from a newspaper. Geng takes this 50-year-old tradition and puts a wacky, ``Saturday Night Live'' spin on it. She's collected 24 of them in her recently released second book, ``Love Trouble is My Business'' (Harper & Row, New York, $15.95).

One discusses weapons in the voice of a French wine critic: ``If the label also says `Mise en bouteille au Directorat G'en'eral de S'ecurit'e Externe,' you have a first-class Nuage, partaking of the typically delightful fruitiness, thirst-quenching fra^icheur, and vivacious charm evoked by the Beaujolais bottle, yet boasting complex overtones of the aromatic wood pulp and potassium nitrate used as an inert base or adsorbent to balance the acidity of the nitro.'' She got that one by finding two clippings: one about wine, the other about an investigation into the July '85 sinking of the Greenpeace ship Rainbow Warrior in New Zealand. Both pieces were written by the same wine correspondent.

Geng, who writes casuals and edits fiction at The New Yorker, has also published in Harper's, The New Republic, and The New York Review of Books. She seems to be a human vacuum cleaner for various voices: She'll write in a hard-boiled detective-novel style, in an articulate but self-justifying yuppie voice, or in the mode of simpering wedding announcements. Her ``straight'' reportage is so believable that others have mistaken it for fact. The New York Times Book Review called her a ``devastating witness of present-day mores.''

``I admire her extravagantly,'' says Anne Bernays, a Cambridge, Mass., novelist. ``Her humor is the opposite of broad, it's like a diamond stylus. She has a dazzling imagination, and what she has tried to do in other pieces is to be a ventriloquist and a satirist, so she takes on the tone and voice of the things she's satirizing.''

All of Geng's protestations of normality aside, she seems to have a knack for just stumbling across the ridiculous, then developing it. Like the $87.25 bill for boarding a defense contractor's dog she read about in the probe of Pentagon spending. In her piece, ``Canine Ch^ateau,'' that fact is transformed into a fictitious letter to Caspar Weinberger from the bristling kennel owner:

``Catalina Suite: $280. If it seems a bit steep, consider that each suite is actually an individual bunker, deployed with gyroscopic mounts on an elliptical underground track and activated to a speed of 35 mph by random changes in the earth's magnetic field. This is a security precaution and, we feel, an essential one.''

Where does she get this stuff? Oh, everyday reference books people have lying around, such as a 1917 artillery manual. But she doesn't consider herself a bloodhound of absurd facts. ``I don't think you'd ever think of anything if you were like that,'' she says. ``The ideas like to pretend you're not looking. My friend [New Yorker writer] Ian Frazier once said, `You can't really write a casual, you wait for a casual.'''

GENG reads in a Ronald Reagan speech that Clare Boothe Luce says history will give all presidents only one sentence. So she obligingly writes what she feels should be their one sentence:

Benjamin Harrison: ``He predicted the birth of the Dionne Quintuplets over 40 years before it happened.''

Herbert Hoover: ``He reorganized the National Christmas Card Cemetery.''

Warren G. Harding: ``He campaigned on a bicycle carved from a single giant bar of soap.''

Geng attributes her sense of ease with serendipity to her parents' reading ``Alice in Wonderland'' to her from the age of 2. ``I loved it and insisted that it be read over and over,'' she says. ``I think it had some effect on my sense of humor, a sense of illogic and how funny illogic is. That, and the paperback collection of the Watergate transcripts, are my two favorite books. They're not unlike each other.''

WOLCOTT GIBBS, an early New Yorker writer, was another early influence. ``He would look for public statements that something didn't exist and then make it up. Like, `There are no funny anecdotes about Calvin Coolidge.' He then wrote a whole perverse series of anecdotes. I thought, `Oh, I could do this.'''

Some of her more ambitious pieces would never have been written if Donald Barthelme, the satiric novelist and short-story writer (``Come Back, Dr. Caligari,'' ``Snow White,'' ``Unspeakable Practices, Unnatural Acts''), hadn't invented a new way of writing fiction in the late '60s and early '70s, she says. ``It was a whole way of using benign, abstract, funny, personal things, a whole constellation of things that interest you at the moment that fiction writers find hard to use.''

Written humor has become rare, she says. ``I think there aren't as many people doing it now, and I don't know why. Maybe that's a function of where you can publish it. There were more magazines then.'' Or it may just be the times. ``Everybody always says the same thing: `Oh, the world has become so much more lunatic today that it's hard to write anything more preposterous than the reality.'''