Were you ever bored? Did you find your mind wandering? Can you tell me where in the story this was happening?
What did you think about the character named XXXX? Did you like him? Hate him? Keep forgetting who he was? (Same for all the major and minor characters.)
Was there anything you didn’t understand? Is there any section you had to read twice? Is there any place where you got confused?
Was there anything you didn’t believe? Any time when you said “Oh, come on!”
What do you think will happen next? What are you still wondering about?