I guess I cringe when the discussion leads to, rather than books and sentences and characters and the stuff that writers are supposed to be concerned with, how to have an online presence and how many followers you have on Twitter. That stuff always makes me uncomfortable.
Right away I think of two books - 'Wuthering Heights' and 'Rebecca' - and of just sinking into them as a young reader. I think they must have appealed not just to my romantic adolescent soul, but I suppose there's also an appealing darkness in both of them.
My own 'sentimental favorite' is always the novel I haven't yet written - I suppose that's the one I consider my 'masterpiece' as well.