THE RUSTLING OF PAPER, and the resounding middle- C of chairs scraping against the floor. A door slams in a far-off alcove, and every now and then, a book closes with a quiet "mupf."

This is the Main Reading Room, the heart of the Library and the home of the main card catalogue -- 23 million cards in all, everything from travel books to textbooks, from popular prose to obscure verse. With major renovation of the Library starting this year, this room is soon to become what the Library calls the "Index to the Halls of Knowledge"! In the new, improved, "Multi-Media Encyclopedia"!

Readers, to rest their eyes, look up, up, up into the famous dome of the Main Reading Room. Statues tower over them like Olympian gods -- issuing the challenges of Shakespeare, Herodotus and Homer. A majestic peace. You sit taller, for this is one of the private places, with an assortment of students of all ages, surrounded by more learning than they, combined, can dream of.

"Some people are relatively satisfied if they just have a place to sit down and some books to look at," says John Broderick, assistant librarian for research services. This is that place.

Ellen Hahn, chief of the general reading rooms, says your library life will be easier if you first exhaust the resources at your county or university library. It may actually have the books you want. If you need help formulating a research question, work with your local librarian. Then take your question to the Main Reading Room, stopping at the Research Guidance office just inside the room's main entrance for any additional help.

If all you want is books, reserve yourself a desk by hanging your coat on the back of the chair, look up the books' call numbers in the card catalogue or the moderately user-friendly computer catalogue, fill out the call slips, hand them in at the central desk, and wait.

And wait.

Some read paperbacks like "Fatal Vision" or listen to a Walkman. Some while waiting lose themselves in the tunnels that connect the library's three buildings. Often, by the time they return from coffee in the snack bar, books have miraculously appeared.

Signs at the book-request desk tell how long a wait -- could be 50, 60 minutes, depending on what building holds your books. Could be forever, if you forget to write your seat number on the call slip.

Recently, to test the Library's retrieval system, a reader took a random and totally unscientific sampling of 12 book requests. Herewith, the results.

Instead of the "Belgian Coast Holiday Guide," the walker who hands out the books dropped off "Oostbrabantse Plaatsnamen." Hey, nice try. The call numbers were very close.

"Leap in the Dark, a Romance," arrived with a pant. Also appearing quickly was "The Family of Bumbel Bees," by S.M. Zzizinga, chosen for being the last card in the last drawer of the card catalogue.

Complete with apologies from its 81-year-old author, "Mrs. Shakespeare's Second Marriage" came in pristine condition. (If books are souls that can be lost, I have done some good today.)

Two slips returned without books: the one for "Florida Vegetable Crops" was marked insufficient date (the reader's oversight). "Prairie Peril" wasn't on the shelf. But mysteriously showing up was the thoroughly unwanted "Proceedings of the Biological Society of Washington."

In all, the Library retrieved 75 percent of actual requests, and it likely would've hit 83 percent, if the reader had filled out all the call slips right.