A MAJOR REFERENCE WORK, not only for science fiction, but for literature in general, has just emerged from Great Britian. Prepared by a team associated in various ways with the Science Fiction Foundation of North East London Polytechnic, The Science Fiction Encyclopedia (Doubleday, $24.95; Dolphin paperback, $12.95) is an enormous volume that has almost -- but not quite -- everything that a fan or researcher could wish.

To cite figures, since it is otherwise difficult to convey the exhaustive nature of this book, the Encyclopedia contains about 700,000 words and about 2,8000 entries. It has bio-bibliographic articles on some 1,800 authors and editors, with critical and historical comments, and it offers life histories for more than 200 magazines that have printed sf. It describes motion pictures, television series, comic strips and books, illustrators, specialist publishers, and even sf fandom. More than 170 essays are devoted to important sf themes and ideas, while many articles cover the early history of sf, the American creation of modern sf, its diffusion abroad and other national traditions.

While 35 contributors are listed, more than three-quarters of the book has been written by the general editor Peter Nicholls and his associate editors John Clute, Malcolm Edwards and Brian Stableford (with technical assistance from Carolyn Eardley). Theirs is an enormous achievement, done, for the most part, very well. The editor-authors have hit highpoints with percision and economy, have handled historical matters with sensitivity and common sense, have made apt criticisms and have placed science fiction in its cultural contexts.

The Encyclopedia is unquestionably the most important work that has been prepared inthe field of fantastic literature, and it is sure to remain the standard work indefinitely. Certainly no individual can ever compete successfully with a team as knowledgeable and as skilled as these four Britons and their assistants.

Yet, superlatives aside, this book does have limitations which must be mentioned. There are a few errors in dates, but in a work like this an occasional misprint is inevitable and forgivable. A more significant weakness, however, is to be seen in many of the shorter articles, which are not always on the same high level as the major entries. The wrong books are sometimes memtioned; themes are missed; and easily obtainable dates are omitted. The overall point of view, too, is sometimes insular, and the editorial penchant for tossing about simplistic political divisions is sometimes mildly annoying.

The selection of entries is not always above reproach. You will find entries for very minor British authors, about whom all that can be said is that they wrote one or two "routine" novels. But you will not find entries for Charles F. Tiphaigne de la Roche (creator of the most remarkable prophetic inventions of the 18th century); Philip M. Fisher (a very important Munsey author); Gilbert Murray (the classical scholar and author of an excellent lost-race novel); J. S. Nicolson (economist, author of three important Victorian sf novels); Mrs. L. T. Meade (the foremost turn-of-the-century writer of scientific mysteries); and many others. Strangely enough, Clark Ashton Smith is included for his weird fiction, while his sf, which anticipated modern work in its sexual and metaphysical concerns, is not mentioned. A certain amount of material about fantasy has been included, because, as the editor says, the sf readship overlaps with that of fantasy. Including such material was an error, since the treatment is spotty and without the authority of the sf coverage.

Still, these flaws are but dust on the crystal, and are far outweighed by the virtues of the book. The Encyclopedia remains a work that should be available to everyone seriously interested in science fiction.

Within the past five or six years the publication of adult fantasies has boomed, perhaps to the point of impending overkill. The paperback stands are crammed with dragons, muscular swordsmen, clinging or frisky heroines, wily wizards and magic that Dr. Faust never dreamed of. Some guidance to this field has become necessary, since new authors keep hatching out and old authors keep writing interminable series-works.

Fantasy Literature: A Core Collection and Reference Guide (Bowker, $14.95) by Marshall B. Tymn, Kenneth J. Zahorski and Robert H. Boyer is the first major survey of modern high fantasy, although there have been a couple of less ambitious predecessors. It contains an overview of reference material (by Tymn) and 240 detailed plot summaries and analyses (by Zahorski and Boyer) of books mostly from the modern period.

These nicely written summaries are fairly long, convey the flavor of their originals well, offer background and make many good critical points. But it should be noted that the authors do not always mention subsurface themes and techniques, Fantasy, historically considered, has always been rife with allegory and deliberate symbolic devices, and some books need comment about events below the story line. It would have been better, for example, to have mentioned the elaborate structuring and equivalences of James Branch Cabell's Jurgen , even if modern thrill-readers do not care about such things.

Nonetheless, Fantasy Literature is a useful book for the fan, collector, librarian, or even for the author seeking ideas. But I must confess that I would not consider the selection of books entirely suitable for a core collection.

For readers new to science fiction Baird Searles and his colleagues Martin Last, Beth Meacham and Michael Franklin have prepared a clear, well-organized introduction to current books. A Reader's Guide to Science Fiction (Avon, $2.95) covers 200 authors alphabetically, with brief comments about a couple of important works by each author. It is gracefully written, and it carries the reader along lightly and easily. Searles and his associates, however, are out-and-out paperback modernists, and they do not venture much into the older literature. When they do, their estimations lack the empathy shown for current books. In addition to the author entries, there is a system of cross references to suggest a reading program: "If you like A, try B." The system does not work for me, but it may suit others. All in all, Searles' book will help ease a beginner into a complex area of popular fiction, though more discriminating readers may come to distrust Searles for his tendency to glow with enthusiasm about almost everything -- except Harlan Ellison, who is treated sourly. Praising everything really amounts to praising nothing.