How can I set boundaries without being a jerk?

If you value this book so much, why on earth are you carrying it around in your backpack and laying it down places?! Treasured things need to be kept where they cannot be touched. So, read the thing at home and frame the pic and put it on your wall, end of problem. If you keep it out, expect others to want to touch it. You are being unreasonable. If you put a diamond necklace or a gold buillion on the desk, people would want to touch those too, over and over.