Medical students are not expected only to read medical books, and the interviewers understand this. They want to see if you are the type of person to read for pleasure, and if so, what interests you. If you do not enjoy reading during your downtime, describe other ways you stimulate your mind, such as listening to podcasts. Also, be sure if you have read a work of fiction recently, that it is not something that would offend or embarrass the interviewers. If you enjoy reading, describe the most recent work of fiction you have read and give a brief synopsis.