AS THE book as we know it in danger of extinction? You might have gathered that from a story in The Post this week on the computerization of the Library of Congress. There are people involved in that work who see a future when the many thousands of words now contained in a book such as "War and Peace" will be compressed into a glob of data to be called forth whenever desired from some faraway central storage space and read on a video screen instead of the printed page. Books will be for museums.

Traditionalists are understandably alarmed at this prospect. They needn't be. Video screens are not going to replace books. Here are a few reasons why:

You cannot read a video screen lying on your stomach.

You cannot stack up several video screens to hold a door open or put a crease in your pants.

You cannot mark your place in a video screen with a carrot or a banana peel.

You cannot inscribe on the inside cover of a video screen, "To my dearest friend, with deep and heartfelt appreciation for all you have done for me" and then two years later find it on a table at a rummage sale, marked "50 cents."

If you leave a video screen on a rocking chair on the front porch it will be stolen. If you try to read it in the bath you will be electrocuted. If you throw it at your cat it will be destroyed (the video screen).

You cannot break the silence in a room by slamming a video screen shut and exclaiming, "This man is a damn fool."

You cannot dog-ear corners on a video screen to mark the dirty parts.

You cannot stand in a pulpit and read Scripture from a video screen with anything approaching the proper degree of reverence.

Used video screens, because they do not smell properly musty or have any intrinsic interest, will not be resold by eccentric people who run cobwebby shops in low-rent buildings. Instead they will be thrown in the dumpster. In time, perhaps, it is they rather than books that will become extinct.