What is a good question to ask someone about a book ?

what is a good question to ask someone about a book ?

All good stories contain a conflict. For example a girl and a boy love each other but their families disapprove (Romeo & Juliette). A whaling ship strays from it's primary purpose because the captain is fixated on finding the one whale that maimed him ( Moby Di*k). An idealistic German soldier is disillusioned by the horror and utter waste of war ( All Quiet on the Western Front).
In each story a conflict is introduced. How the characters react to this is what makes the book interesting. Will they be noble or petty or withdrawn to inaction. That is the human drama the drives the story. But first the author must set the scene.
What you must do to understand a book is to first identify the conflict. Than you can discuss the course of action that follows. When you get really good you can introduce other feasible plans of action and enlarge upon the story with your own original thoughts.

How about what did you think of the book? Was it a fun read, interesting plot, decent story, etc?

"Is it YOUR book?"
"Would you like to read it ones more sometime to understand it deeply?"
"What do you think: does this book worth talking about it?"