I think there is a difference. "Is it good?" is a completely neutral question. The speaker is not indicating whether they have any preconceptions as to the quality of the book. "Is it any good?" is not such a neutral question. Whenever we ask a question with 'any', we have in our minds the counterpart of 'any', which is 'no'. So, when we ask "Is it any good?" we are alluding to the possibility that there might be nothing good about the book, and we are asking the other person to say whether or not this is true. The difference between the two is subtle, but it's there. Look at it this way ... imagine you had written a book. You would be far more insulted by the question "Is it any good?" ( with the implication that the speaker expected it to be rubbish) than by the straightforward question "Is it good?".

That is a good question! I'm not sure if my advice would be any good but I can try. Is the new employee any good? Is the weather going to be good tomorrow? Was the film any good? more likely to hear this (worth watching ) Was the film good? less likely to hear (above average). i interpret any good to be a lower bar of being true. Maybe think of; any good = not bad. good = better than average.

That is a good question! I'm not sure if my advice would be any good but I can try. Is the new employee any good? Is the weather going to be good tomorrow? Was the film any good? more likely to hear this (worth watching ) Was the film good? less likely to hear (above average). i interpret any good to be a lower bar of being true. Maybe think of; any good = not bad. good = better than average.

Yep I agree with Drew (I'm also a native). It's a very very subtle difference, and one that ultimately doesn't change the meaning or the answer that will be given.

Wow, I'm a native English speaker, but this is pretty subtle. The easy answer is: There is no difference. You could use them interchangeably and no one would think anything of it. I suppose "Is it any good?" is less formal and less literate. You would ask this in an off-hand way, as if you really didn't care much about whether the book is worth reading or not, because you are not planning to read it anyway. On the other hand, "Is it good?" could go either way. It could be just a casual question for the sake of conversation, or it could be a sincere request to learn something about the qualities of the book. By the way, I haven't read The Idiot. Is it any good?