IF YOU REFUSE to go to anything that isn't The Greatest Show on Earth, you miss a lot.Tucked back in Room 256, the Rare Book Division of the Library of Congress, is a show that consists of exactly 28 items. They're just books. And they're not even very ancient, the oldest dating from 1904. You can go through them in a half-hour, and maybe it won't change your life or even raise your blood pressure, but it's pleasant.

These are American books, celebrating the return to fine printing that William Morris inspired in England with his Kelmscott Press at the turn of the century. Printing is one of those arts that seems to have been perfect at their conception, as curator Rob Shields put it, and forever after the struggle is to do something as fine as that first masterpiece, the Gutenberg Bible. Certainly in the 18th and 19th centuries people became so excited with the new toys of mass production that they forgot craftsmanship and went for the quantity. Morris and others started us on the road back.

For some years now, a small renaissance in fine book printing and binding has been rushing around this country, evidently starting in San Francisco in the '50s, soon spreading to New York and all over. Each tiny press seems to have its own specialty.

Some print the classics, some publish new young poets (who often turn out to be the printers themselves). Some make their own paper. Walter Hamady's Perishable Press published some William Stafford poems on a beautiful pale blue paper made from the printer's "love-worn bathrobe."

Many concentrate on the illustrations. Thomas Cleland invented a new silkscreening process simply to get the right look for the pictures in a 1958 edition of Prevost's "Manon Lescaut." It took him six years. The effect is of a delicate watercolor by a somewhat cynical Fragonard.

One of the pleasures in this exhibit, which opened last week, is studying Gaudy's sketches for an illumined letter and even for a dingbat, that curious pollywog used by printers to end a chapter or set off a title. Who could imagine spending hours at a drafting table, measuring, erasing, redrawing, to give the world a new dingbat?

Merely to lean over the cases and study the spread-out pages is pleasure enough. The clean bite of black, black type on white, white paper, the crisp edges of each elegant letter, each comma and period, the glistening of the ink, the texture of the handmade paper: "It's so soft you really want to touch it," said reference and reader services director Peter Van Wingen.

He pointed out an oversize new version of Allen Ginsberg's "Howl" by Grabhorn Press. It was the kind of production that challenges a poem to be worthy of it. Even the cover design was intricately stippled to form the title.

Some of these books are printed in as many as 500 copies, some in as few as 25. For collectors they are strictly a speculation. But a pretty one. Look at the Labyrinth Editions' version of William Everson's "Eastward the Armies." Put together by Richard Bigus when he was a graduate student at Yale, it does what he had set out to do: "make poetry as concrete as possible . . ."

It's not just the lush, thick margins, the palpable paper, the sure, spare line drawings, the stately march of clear, black letters across the page. The appeal is in the whole thing, in the love and attention that made this happen.