No one doubts that a California book "slicer" who has cut more than 20 stacks of books in several northern California libraries this year is a book mutilator. The vandal, still at large, has ruined about 200 books, and the loss exceeds $10,000.

      Yet a more subtle and less publicized form of vandalism occurs in libraries every day, says Brigham Young University librarian Larry Ostler. People regularly mar library books by underlining and making notations in them."Students have become accustomed to marking their own textbooks, and that tendency to underline extends to library books," he says.

      Although marking a book creates varying degrees of damage, the real problem, he says, is that meaning in a book changes when someone marks it.

      "Look," he says, holding a book with pencil marks that create an outline and prominent areas highlighted with a yellow marker. "It is impossible to ignore the markings, isn't it? It changes the way the material is viewed, how it is perceived and even how it is valued.

      "When someone marks a book, what they are really doing is changing the text."

      Although the BYU library does not have an aggressive campaign to locate offenders, Ostler believes writing in books is increasing, and that patrons need to realize the damage is deeper than the marks.

      "We used to discover a couple of students each year who had marked their library books, and that number is now about 70. We find many clues at the check-in desks. Our interest in catching people is in letting them know that their behavior results in more than just marking up the books. We're interested in increasing awareness."

      He showed two damaged books. One came back with a series of BB gun holes through every page and the other - a thick book on automobile repairs - was covered with grease.

      "People know they have done something wrong when they return a book as damaged as these are," Ostler says. "I just want people to realize that although a pencil is not as damaging as a pen, and a pen is not as harmful as a highlighter, any marking rearranges the text and profoundly changes how the next reader sees the text. Besides, our era of copy machines, scanners and color copiers offer good alternatives to writing in a book."