UNTIL rather recently Latin American literature was simply not a topic thought worthy of conversation in New York publishing circles. While the popularity of Gabriel Garcia M,arquez and One Hundred Years of Solitude, brought out in English back in 1969, did open some people's eyes, it wasn't really enough. Thus, in 1976, when translator Thomas Colchie -- already gaining a reputation comparable to Gregory Rabassa's and Helen Lane's -- decided to set himself up as an agent to represent Latin American authors, it was viewed by the industry, he says, as a "picaresque" and ultimately "hopeless" venture.

No longer. The important but heretofore missing element -- what Colchie, a 41-year- old New Yorker, calls "context" -- fell into place in 1980. It was then that Avon Books published an original novel by Brazilian writer Marcio Souza, Emperor of the Amazon (with Colchie as translator and agent) to loud critical cheers and, even more important, to impressive sales figures. Avon, of course, had already ventured into Latin American fiction under its Bard imprint; this effort was an attempt to capitalize on the enormous and continued success of Garcia M,arquez. Yet he had remained the only author with large audience acceptance. With Marcio Souza a phenomenon made the transition into a trend.

"That launched me, suddenly, as an agent all over the world," recalls Colchie with obvious pleasure and no little relief. Before that, he'd "persisted, placed a few books," but, basically, experienced "five years of hell . . . or poverty." Now there were editors on hold, waiting to make deals involving Spanish and Portuguese writers whose names they could barely pronounce. Colchie, who himself translates from both Spanish and Portuguese (Manuel Puig's Kiss of the Spider Woman, Murilo Rubiao's The Ex-Magician and Other Stories and others), had to begin "to look for younger translators," for whom, as their agent, he insisted on royalties and a percentage of the subsidiary rights. Like the Latin American literature they worked on, translators had too long, Colchie felt, been treated as stepchildren.

What are his current projects? There are four more Marcio Souza novels in the pipeline, including Mad Maria, due next next spring from David Godine in hardcover and Avon in paper, and Orders of the Day, a science fiction parody, six months after that. Carlos Franqui's nonfiction Family Portrait with Fidel (Random House), a recent release, is his, as was Manilio Argueta's One Day of Life, which kicked off the Aventura trade paperback line. And he's helping to launch another new imprint, Ballantine's innovative Available Press, having sold Centaur in the Garden by Moacyr Scliar. (Here Colchie's working once again with Robert Wyatt, whom he first knew at Avon and who has, he says, "the best understanding of what to do with Latin American literature.") Of this novel about a centaur who's both Brazilian and Jewish, Colchie says simply, "It's my most extraordinary find so far."

Beyond his annual trips to Latin America in search of new contacts, Tom Colchie is currently passionate about introducing Portuguese and Portuguese-Angolan writers to English readers. "I'm having the same problem as when I first wanted to publish Brazilian writers. Without awareness, things fall into too-easy slots." Horror and the Law

WHEN lawyers have hobbies, they often tend to be trendy ones like running marathons or gourmet cooking, things that can be easily talked about during the firm's annual retreat. That's why Douglas E. Winter, of Washington's Covington and Burling, who writes widely about horror fiction and spends time hanging around with Stephen King, has to endure some puzzled looks from his colleagues. Perhaps, though, they'll understand better, if they browse through some of Winter's books. One of them, published originally as a critical monograph in a small press series, has been enlarged and updated for release by New American Library in November. Called Stephen King: The Art of Darkness, it's part critical analysis, part extended interview with the author.

Others Winter has done or is doing are Shadowings: The Reader's Guide to Horror Fiction 1981-82 (Starmont, P.O. Box 851, Mercer Island, Wash. 98040, $6.95), an upcoming Berkley collection of conversations with 16 horror writers (including King, Peter Straub, William Peter Blatty and Ramsey Campbell), and Demons by Daylight, a King bibliography which will be released by Donald M. Grant, a small Rhode Island publisher. Moreover, Winter has been signed to write the script for a television documentary on horror, a book on Peter Straub is in the works, and there are currently negotiations for him to edit a "major" anthology of comtemporary American horror writers. This last, he says, will represent "the cutting edge of modern horror" and be comparable to Harlan Ellison's seminal science fiction collection, Dangerous Visions.

The horror community, though, Winter says, "is much different from the science fiction one, in that they've nothing to prove." But, he adds, "You can't be into horror fiction and not be ambivalent about it." Now 33 and a graduate of Harvard Law School, he explains that his first strong sensation of being deliciously frightened came after seeing the original Invasion of the Body Snatchers: "That night I dreamed all my friends, my parents, my brothers were being replaced."

His schoolteacher mother, Winter remembers, encouraged him in this special interest by buying a subscription to Famous Monsters of Filmland. And, in second grade, he started to write his own novelizations for the bizarre Japanese creature features of the period like Rodan and Godzilla. "Growing up with horror," Winter remarks, "the big change came with Psycho. It's okay to have a rubber monster playing hopscotch on Tokyo, but when it's your next-door neighbor, it's not so much fun anymore." Side Bets

WASHINGTON writers, like writers everywhere, frequently complain that their books aren't being stocked at local shops. Now along comes a new bookstore, Politics and Prose, on upper Connecticut Avenue, "where a Washington area writer can be assured that his or her book will be carried." That's a hefty promise, but owner Carla Cohen, says she intends to keep it. "I want to keep everything in stock," she vows, at the same time stressing that Politics and Prose "isn't a museum. If something just doesn't sell in six to nine months, we'll have to send it back." Calling her venture a "full-service bookstore," Cohen says that, as the name implies, emphasis will be on public affairs and literature, what she terms ''thoughtful books." . . .

Twenty-one printings after its original June 1983 press run, Alice Walker's The Color Purple now has over 1 million copies out in its Washington Square Press trade paper edition. Walker's newest collection of poems, Horses Make a Landscape More Beautiful (Harcourt Brace Jovanovich) being published this month, is the fourth book of poetry she's done. The first, Once, came out in '68, and it's been five years since the last, Good Night, Willie Lee, I'll See You in the Morning . . . .. This fall, in addition to Congressman Claude Pepper's (D-Fla.) resource guide for older Americans, Ask Claude Pepper (Doubleday), there's another well-known name with advice on aging. The Best Years of Your Life, a new Villard title, is by Dr. Miriam Stoppard, who is herself not only a well known British expert on medical matters but also the wife of playwright Tom Stoppard. Her earlier Day-by-Day Babycare was published by Villard in 1983 and Being a Well Woman was an '82 Holt offering. . . . . Secret Agenda, the new look at Watergate by Washington writer Jim Hougan (Random House), has had some postponements since last spring, when it was first scheduled. Now, however, both the author and his publisher say it's definitely slated for November 12, although there will be no galleys -- according to Random's Cheryl Merser -- sent out prior to publication.