July is the month when I try to clean out the bookshelves, and each year I am struck more forcefully with the duty imposed upon us by the revolution in book publishing.

In my youth, books were treasured and preserved, all of them, or at least nearly all of them. My children, on the other hand, treat them in about the same fashion as, when they were younger, they treated a toy that was broken or that no longer gave pleasure. My sense of values is offended, but logic tells me that, to some extent at least, they are reacting naturally to the law of supply and demand.

In the world before the last great war, American publishers produced fewer than 200 million books each year. Last year, they produced 1.36 billion . Books are everywhere available; they are no longer items of great value, and the paperbacks that came into their own after the war are often read and left, loke yesterday's newspaper.

So my tendency to deplore the conduct of my children is plain old-fashioned, as is my disappointment each year when, after bundling up the books that can no longer be accommodated on my shelves and taking them off to the public library, I find that there are many among tham that the library doesn't want, I come home again, still bearing books, and, with a prayer for my mother, who would have been appalled, I throw them in the frash bin.

I suppose that somewhere in this land there exists a man or a woman who would be pleased to receive a copy of a certain book on potential danger points in foreign policy, which begins as follows, "One of the leastknown but potentially most sensitive examples of cartographical disfiguration is the case of the Afghaniztan-Pakistan-Iran border and where 22 million Phistu and Baluchi tribesmen live in traditional homelands that straddle formal political frontiers."

But I do not know where that man or woman is, and if the public llbrary doesn't want this book - perhaps it already has a copy - what else can I do except throw it away? Think of the work that went into it; think of the feelings of the author; think of what your mother would say; then throw it away.

It would surely please our founding fathers, who cared greatly about the dissemination of popular information, if they could note what a nation of publishers and readers we have become. Last year alone, more than 40,000 new and old "titles" were published.

But there are penalties to be paid for this revolution. It has become impossible to keep up with what one "ought" to read. The late Justice Oliver Wendell Holmes speculated just before he died upon the dread possibility that St. Peter would ask him if he had read such and such a work and, depending upon his answer, might judge him as failing in his duty to keep up with his times. But that was before World War II. Today, a man of Holmes's dedication to that particular duty would be stark, raving mad.

And librarians report that the proliferation of books has led to a carelessness about them that they properly deplore. I do too. My son Nicholas was going out the door on his way to school just a month ago when I noticed something familiar under his arm. "What book is that?" I asked him, and he answered, "The teacher said to read some poetry, and I found this in the living room."

To my horror, he was bearing with him ' perhaps to lose on the bus, or leave on the table after his lunchbreak - an autographed copy of a volume by Robert Frost.

Which is a reminder that there are books to be noted, books to be read, books to be discarded and books to be kept. The revolution in book publishing ought, unlike some other revolutions of our time, impose upon us the arduous but pleasant obligation of choice.