So are you saying I should leave them like that? I shouldn't overlap UVs (one of the rules they drilled into our heads at school) and if I leave them like that wouldn't it be kind of a big disadvantage that I will have a lot of uv space that is not visible and which will result in a lower res texture?

edit: ok I think I kinda realized what you're saying and I want consistency, I want the texture of the book on top to be the same res/detail as the one on the bottom.