WELCOME TO the dark recesses of the public library's overnight book drop, depository for the mute evidence of a thousand little crimes committed day in and day out by otherwise law-abiding citizens.

Here lies the book in which a strip of bacon has been used to mark the place. Here is a volume in which every single page has been bent down at the corner, and here the opera record album that was left on a hot radiator to become hideously warped. Here is the cookbook spattered with spaghetti sauce, and here the canine obedience manual, chewed to shreds. And over here, in a dark corner under 14 pounds of Micheners, lies a book that is approximately 100 years overdue.

One hundred years? Yes, give or take a few decades. The book, a volume of British laws enacted in the mid-17th century, turned up this week in a drop bin at a public library in Harrisburg, Pa. It was, as it turned out, part of a purchase for the Pennsylvania General Assembly that had been made under the direction of Benjamin Franklin. The book was evidently taken out of the Pennsylvania State Library sometime between 1823 and the beginning of this century. The library is unable to be more precise, although the consequences so far as the fine is concerned would be -- at 10 cents a day -- considerable.

Perhaps in time we'll learn the identity of the reader who returned this volume. It would be interesting to see what he had to say for himself. Most of us, in pleading to have our fines reduced, make the most pitiable of excuses to the librarian on duty: "My kid was sick but I would have gotten the books in last week except the car broke down and then it was so cold the pipes burst but that was before my aunt flew in from Toledo and we had to . . ."

But consider the rich store of excuses available to the phantom reader of Harrisburg. "Do you want me to begin," he would ask the librarian, "with the Civil War, the great flood of '89 or the night I was looking at Halley's comet and ran my buggy into a ditch?"