Translation:Please do not return the book yet.
Maybe your friend checked out a book from the library, and you want to read it before they return it?
I ran after my friend.
"Please do not return the book yet!"
"Why?" He asked.
I took it from him as I said:
"I left my ID inside it!"
Unfortunately I can not explain academic rules. I have used it every day without thinking. However, it seems like a quite difficult mechanism. Please refer to the following and do your best.
まだ is one of the things that comes before the thing it's referring to. In this case, you refer to returning the book
Why do some of these sentences accept the translation without "please" while others don't? Shouldn't both be accepted in most cases?