1) Dog Eared Books
This always drives me crazy. I know a lot of people do it to save their page, but I can't stand it. Whenever I come across a page that has been dog eared I compulsively have to flatten it out. If you want to mark your page get a bookmark, they make a variety of them. You can even use a scrap of paper if necessary.
2) The Book Borrower that Never Returns the BookThe key word is borrow. I'm letting you borrow my book, I'm not giving it to you. You can't keep it forever. I'm one of those people who will read books over and over, so eventually I will want to read my book again which is hard to do when I don't have it. If you like the book so much, buy your own copy.
3) The Over-The-Shoulder Reader
I don't like people leaning over my shoulder for any reason. There is such a thing as personal space and if I can feel your breath on the back of my neck, you are in my personal space. It's uncomfortable having someone leaning over your shoulder reading what you're reading. Reading isn't a group activity, if that's what your looking for go join a sports team.