If you've got more books than shelves to put them on, you could rummage through your collection and donate the rejects to the handiest good cause. Or you could do what Stanley Marcus did. When the Dallas retail merchant ran out of wall space for his book collection about 10 years ago, he simply started buying miniatures instead. More than a hundred of Marcus' tiny tomes are now on exhibit in the Great Hall of the Library of Congress.

Miniature books have been around for centuries and for a wide variety of reasons, as the books on display demonstrate. They range from a 1545 French prayerbook to an 1825 illustrated edition of Shakespeare's works to World War II propaganda leaflets. None is more than three inches in height, and most can be read with the naked eye - if you have good vision, cautions John Chalmers, a rare-book specialist at the Library.

The smallest book on display is an 1896 edition of Galileo's A Madman Christina Di Lorena , printed in what's called "fly's type," the smallest ever cast. The book measures no more than about 3/4" high, and is about as thick. It's said to be the smallest book printed from movable type.

Not all the books are exotic. Many were desgined for purely practical reasons. Stage-coach passengers carried miniature timetables in their pockets, much as we carry bus schedules today. Little pocket almanacs, for looking up things like the phases of the moon, church festivals or lists of government officials, were extremely popular from the mid-17th century to the 1920s. And for computing percentages, merchants carried handy conversion tables - sort of an early versions of the pocket calculator.

The exhibit is open daily 8:30 to 6 on weekends, and until 9:30 weeknights, through May 8. And if your own bookshelves are feeling the pinch, you can get started on miniatures by scouting antiquarian bookstores - listed in the Yellow Pages under "Book Dealers, Used and Rare."