Kafka wrote, in a letter:
If the book we are reading does not wake us, as with a fist hammering on our skull, why then do we read it?
So that it shall make us happy?
Good God, we would also be happy if we had no books, and such books as make us happy we could, if need be, write ourselves.
But what we must have are those books which come upon us like ill-fortune,and distress us deeply, like the death of one we love better than ourselves, like suicide.
A book must be an ice-axe to break the sea frozen inside us.