This 'getting to know you' question provides insights into your personality. However, when things relax in an interview, keep your eye on the big-picture. Remember why you are there. It's up to you how you want to present yourself in this opportunity, so take care of want to say about yourself. Show the interviewer that you feed your mind regularly. Your answer doesn't necessarily need to be a book. It could be a paper, a study, someone else's thesis, anything. It could also be a work of fiction if what you're reading is for entertainment value. However, you should share something at a collegiate reading level or higher. Impress by suggesting you're reading multiple books simultaneously with ease.