Every time a candidate would put a word “reading” into the hobbies section on their CV, I really loved to ask this question. I am myself a voracious reader, and I love a good discussion on books – so, I would definitely ask a candidate in the beginning of an interview what is his or her favourite book or what is the good book that they’ve read recently. So you better have an answer for this, or don’t put it on your CV :)
As regards to what to reply – of course, there is no right or wrong answer here. Just be honest and authentic, do not make stuff up or mention a book you’ve never read (because your interviewer might have). So, if you enjoy non-fiction and topics like biology and genetics, talk about it. But also if you enjoy adventure novels or modern crime fiction, talk about it. In the end what matters is that you are able to show a bit of who you are. MBB are looking for unique personalities – people who are interesting to talk to, people whose company both clients and the colleagues would enjoy, people who can inspire by their uniqueness. So, do not be afraid to show it :)