THE HORROR BOOM is obviously not over, despite what some publishers have claimed, for good and run-of-the mill books continue to appear -- anthologies, novels, short story collections, and even a few scholarly works.

Among scholarly and reference books Douglas E. Winter's Stephen King: The Art of Darkness (New American Library, $14.95) is outstanding. Winter has become the semiofficial Boswell to King, and his book is a rewarding study of the writer and his work. King is, of course, the leading novelist in the contemporary horror story, and Winter's book is a source that all students will need. It is also well written and can be read for its own literary quality.

For checking the background to much supernatural and horror fiction the first two volumes (A through O) of Leslie A. Shepard's Encyclopedia of Occultism and Parapsychology (Gale, $220 for all three volumes) are now available. The set contains a wild mishmash of topics in comparative religion, biographies of mediums, discussions of parapsychological experiments, medieval demonology, occult secret societies, and much else. It is equally mixed in quality, with some excellent essays quoting documents otherwise almost impossible to find, but also with a lot of dead wood, articles generations out of date, and errors. Many of the articles, presumably written by professional researchers of rationalistic bent, look as if they have been altered to fit the editorial position of utter gullibility. A bad job, I thought, after going through it. But then I had occasion to track down information on occult topics, and discovered to my surprise that in every case the encyclopedia had exactly what I wanted to know. I am now compelled to characterize it as "a very useful book to the person who has the background to judge individual articles and sort the rubbish from the good." It is too expensive for home use, but it is a fine browsing book for a public library, with tales of madness and folly as colorful as anything in fiction.

THREE BOOKS epitomize current types of anthologies: a theme anthology of classical material, a year's best collection, and a small press collection of new material.

Witches' Brew (Macmillan, $19.95), edited by Marcia Muller and Bill Pronzini, is a feminist-slanted anthology drawn from mainstream and genre authors. There are fragments from Ann Radcliffe and Mary Shelley, and stories by Edith Wharton, May Sinclair, Gertrude Atherton, Shirley Jackson, Joyce Carol Oates, and others of lesser renown. (Muller includes a story of her own, which I think demonstrates bad taste and bad judgment.) The general level of the stories is high, and you have more than a 50-50 chance of reading good work. This is a very creditable average. But ignore the introduction and headnotes, which are disastrously sloppy and ill informed. Pronzini, as a mystery writer, should know that Hercule Poirot is not Inspector Poirot, and anyone with the smallest knowledge of the field should know that Mrs. Oliphant and Mrs. Riddell were not early 20th-century authors. I cannot explain the obvious gap between good story selection and ignorance of the field.

Karl Edward Wagner's The Year's Best Horror Stories: Series XII (DAW paperback, $2.95) is the opposite sort of book. Wagner's introduction and headnotes, on which he obviously took pains, are better than many of the stories. One cannot fault Wagner very much for weak stories, for a year's-best anthologist works under disadvantages that other anthologists escape. But too many of the stories present the sensation of d,eja lu. Stephen King, however, has a good sprawling regionalistic story and Ramsey Campbell's "Just Waiting" is a very fine piece of work, which could justify purchase of the book.

The third anthology, Masques (Mackay and Associates, $14.95), edited by J.N. Williamson, contains hitherto unpublished material, much of which, unfortunately, must have come from deep down in the trunk. The big names on the dust jacket may arouse vain expectations, for Charles Beaumont, long dead, is represented by a pointless fragment, Ray Bradbury by three pages of verse, and Richard Matheson by an interview of meager interest. There are two good stories, Gahan Wilson's "The Substitute," the story of a strange invasion, and a horrible conte cruel, "The Alteration," by Dennis Hamilton. All in all, this is a book for a collector of small press publications.

HORROR NOVELS have a special problem -- filling the spaces between the episodes of grue. The Gothic novelists used suggestive landscape and fake history; the high Victorians, domestic detail; but today's writers tend to use either soap opera or explicit sex. Three recent novels do not solve this problem very well.

F. Paul Wilson's The Tomb (Berkley paperback, $3.95) is an updating of the old clich,e of Oriental vengeance, as horrible monstrosities from India invade New York. These are the rakoshi, demon-like beings of fantastic physical prowess, used by a half- mad Bengali diplomat to obtain revenge for a crime committed in India in the 1850s. Against Kusum Bahkti and his rakoshi is Repairman Jack, a hit man with the idealism of the Round Table. There are thrills as Jack confronts the monsters and destroys them, but to get to this point the reader must yawn his way through hundreds of pages about Jack's family life (dismal), his taste in interior decoration (atrocious), and his exploration of the Kamasutra with Bahkti's sister (acrobatic). Is it worth buying a book if you have to skip about half of it? Not for me, but then I'm also annoyed by Wilson's lack of knowledge of matters Indian.

Thinner (New American Library, $12.95) by Richard Bachman fails for similar reasons. There have long been rumors that Stephen King's earlier and weaker work was being published under pseudonyms, and Bachman is widely believed, at least among horror aficionados, to be one such identity. Thinner -- a bad title which evokes the turpentine smell of a paint store -- after extraneous material has been subtracted, is about a lawyer who accidentally kills a Gypsy woman and is cursed into wasting away by the dead woman's father. The basic idea is reminiscent of the historical incident in which the Gypsy conwoman Volga Adams cursed a New York police detective into thinness, making me wonder whether the novel might not have been written many years ago and touched up for the modern market. In any case, it is not good King, although here and there the power of the major King flashes out.

Michael Bishop's Who Made Stevie Crye? (Arkham House, $15.95) is more imaginative and better written than the Wilson or Bachman books. It is a rich mixture of nightmare and bad joke, involving a bewitched typewriter, deep guilt, and pathological hatred. Bishop draws a female protagonist convincingly, and handles transitions between dream and waking beautifully. But the story is repetitious at times and it would have profited by some cutting. Nevertheless, worth reading.

FOUR BOOKS exemplify a trend in modern publishing as small presses boldly issue the short story collections that large commercial publishers claim are unprofitable.

Two of these collections demonstrate the newer ways of writing horror fiction. Things Beyond Midnight (Scream/Press, $15) by William Nolan, who is well-known for Logan's Run, contains 19 stories and a teleplay. The ideas and situations are familiar, but often with an unusual twist. Nolan's sparseness of style is a relief after the verbosity of the novelists mentioned above, but too often his stories read like blow-ups of television scripts, rather than as real short stories. This is piquant when occasionally done, but annoying in quantity. Dennis Etchison, author of Red Dreams (Scream/Press, $15), has a genre reputation as a stylist, and it is true that he is a skilled experimenter with word combinations and presentation techniques. His ideas are sometimes highly original and he has emotional power. But some of his earlier stories seem dated and his obsession with technique sometimes obscures what he has to say.

Two other collections continue the older storytelling ways -- which is perfectly all right. Karl Edward Wagner's stories in In a Lonely Place (Scream/Press, $15) even invoke Lovecraft's Cthulhu cycle at times. In creating background detail Wagner is one of the best genre authors, but he seems to lack a feeling for story unity and has difficulty with form, for otherwise excellent stories fall apart at the ends, particularly in his earier work. Chelsea Quinn Yarbro's Signs and Portents (Dream/Press, $15) tells in a clear rapid manner about personalities confronted with horror, supernatural or otherwise. "Depth of Focus" is a good character study of a swine, and "Savory, Sage, Rosemary and Thyme" is a good witchcraft story, although in both cases the endings are a little hasty.