What would Gutenberg say?

''Never before has the best-seller list been so far from serious writing,'' the literary critic Malcolm Cowley remarked recently, speaking from well over half a century of professional experience.

Alas, his generalization is distressingly easy to support. Take, for instance , the list of paperback best sellers, compiled from the trade by the New York Times. The mid-January list numbered three Garfield titles, as well as three other volumes dealing with cats, including ''The Official I Hate Cats Book'' and ''The Second Official I Hate Cats Book.'' In third and fourth place were two how-to manuals on the problem of Rubik's cube, one by a 13-year-old English schoolboy.

Others among the soft-cover elite: a book of beauty tips, a humorous glossary for sailors, ''The Official Preppy Handbook,'' and ''First Family Paper Doll & Cut-Out Book.''

What would Gutenberg say?

A couple of decades ago a shocked book reviewer coined the word ''non-book'' to describe the literary non-masterpieces that kept tumbling across his desk. It must have seemed then that nothing could be worse than the proliferating volumes on dieting, getting rich, laying brick patios, and so on. But yesterday's non-book reads like today's classic.

''Less than literary'' has become ''less than literate.'' For 10 out of those top 15 best sellers are cartoon books - and we're not even counting the paper dolls.

Cartoons make up the funhouse mirror of everyday life and offer generous consolation. At least one of the cartoon books - a ''Doonesbury'' collection - is a superior work, whatever category it is considered under. But when one registers that two out of three best-selling paperbacks are composed of pictures , it is a little like walking into a museum and discovering that two-thirds of the graphics are formed out of typewritten designs.

There have always been non-books. We all need a little advice from time to time on when to talk to our plants or where to buy a used car or how to jog, or at least walk briskly. But should these non-books, any more than the equally useful Sears catalog, represent the acme of the American reading experience?

Libraries, with the solid Latin word for book (liber) in the name, are turning into audio-visual resource centers. And, at all levels, the old messages of print seem to be reducing themselves to pictures and soundtracks, with a few captions on the side.

Not quite yet on our soft-cover best-seller list is another sort of show-and-tell package. Called the Rhapsody Romance series, here is pulp to keep an eye on. The publishers have designed in tabloid form a hybrid product known as the ''full-length, full-color romance novel,'' reasoning that today's readers crave books that ''carry the visual wallop of a TV program.''

Just as movies are now being adapted into novels, Rhapsody Romances appear to be adapted from soap opera. Models portray the cast of characters on the back cover, and act out scenes within the story. The inside back cover features a final dissolving kiss, with the words ''The End'' printed across it. The lead-in on the front cover reads in the manner of an announcer: ''Halley Beaumont was a weaver of breathtaking fabrics -- but the glittering world of New York fashion threatened to tear apart the romantic dream she wove with designer Gabriel Barring. . . .''

Rhapsody Romances, along with paper doll cut-out books, are extreme examples. We are not suggesting that the future book will be a Sunday newspaper pullout in four colors. The world is not about to regress to the pictogram.

Still, the history of 20th-century communication cannot be read except as a gradual usurping of the kingdom of print. Where readers used to meditate on words, viewers now push electronic buttons. Communication is becoming a spectator sport, and even books are trying to get into the act.

But there are processes of slow and deliberate reasoning that decide our lives, and these cannot be conducted by jet-age logos, layouts, and fast-cut videotapes -- the just-add-water-and-stir forms of instant knowledge.

For the rigors of thought, we still need words in print. Until those pictures that are worth a thousand words can depict even ten words of Plato's Republic, we still need books -- real books.

This is the final message of even the worst best-seller list.