My biggest book habit has to do with dustjackets on hardcover books. I hate them. Love hardcover books, hate the covers. The book gets to the house, comes out of the bag and the dust jacket goes into the trash...immediately. It's a habit I picked up years ago when I would read in bed under the covers and that stupid cover would keep falling off and getting in the way. It was so much easier to just ditch it, so that's what I did, and it stuck. I love the way the books look all lined up, plain colored bindings with shiny writing staring out at me.
Another habit I have is sticking my name on the inside of every book I own. I don't know why I do it, I rarely let anyone borrow them, so it's not like they leave the house. Maybe someday I'll feel like they're old enough to go out on their own and visit friends, at which point tagging them on their covers like a mom writes her kids name on shirt and underwear tags will make sense, but right now it's just a habit that I can't seem to break!
Some people have great book habits. They refuse to fold pages or write in the margins. They keep their books looking brand new for as long as possible. I'm the opposite, I love when my books look all beat up, and used. It shows that they were well loved, which any good book should be! I have some books that are literally held together with duct tape and one very well loved copy of Shakespears complete works that isn't held together at all- it simply lives on the shelf in 3 very seperate pieces.