I'm a complete slob when it comes to books — at least, to books that I own.
I use anything at hand to mark my page (a leaf, a rip of a newspaper, a Popsicle stick). Or I plunk my book facedown, with no concerns about the health of its spine.
And I mark pages. Oh, boy, do I mark pages.
Apparently, I got an early start at it. Cleaning out a bookshelf recently, I came across one of the picture dictionaries we had as kids. I had laid claim to it by writing my name in large, shaky letters across the top of the first 25 pages. In pen. (I also used the blank pages inside to practice my ABCs.)
When I was in college, I filled the Bible-thin pages of my expensive anthologies with hieroglyphics of highlighter (yellow) and cramped notes in ink.
I still have those books, but I can barely read Shelley's "Mutability" or Tennyson's "Ulysses" for all the underlines, exclamation points and indecipherable notes I scribbled in margins.
Ironically, when I gave up pricey new anthologies for cheap used paperbacks, I became a less obvious marker. I became a turner of page corners. A little fold for a nice phrase, a larger fold for a profound paragraph, a double fold for something transcendent.
My new method of marking wasn't out of deference to books. I was annoyed by blots left by the readers who had come before me. I studied their underlines and exclamation points and couldn't find a paragraph worth noting, not even a tidbit of wisdom.