Bitter Apple. It's a clear spray...basically the bitter component of apple seeds in tincture (alcohol). You spray it on stuff, the alcohol evaporates quickly and leaves an invisible but bitter taste on stuff. I learned about it years ago when I had another dog that was fascinated by my books. I did a couple of quick coats on everything lower than waist high. She never messed with them again.
BTW, I'd toss my entire library just to be able to see her again for a day.
Then the Grinch thought of something he hadn't before. What if Christmas, he thought, doesn't come from a store. What if Christmas, perhaps, means a little bit more. ---Theodor Seuss Geisel a.k.a. Dr. Seuss