Not long ago I realized that it is impossible to answer the quesion "What are you favorite books?" because the books you read at the age of 20 might not impress you as much 10, 15, 20 years later. So, basically you can only say something like "Shantaram is one of the best books, and this opinion was based on my reading tastes, outlook and coordinate system in 2015, and I have no idea if I would love it now or not".

Of course, there are exceptions, but overall this rule rings true.