There are those few folks who go that one step further though. For instance, these anal types over at Things Organised Neatly. (I must admit though, the orderly-ness and tidiness of some of these pics does send my Librarian 2 hearts racing!)
You can really go all-out though...
Then again: Hit a pothole or some air turbulence in the BookTARDIS, and the books can all end up like this: