"A book can never be anything more than the impression of its author’s thoughts [Ein Buch kann nie mehr seyn, als der Abdruck der Gedanken des Verfassers]. The value of these thoughts lies either in the matter about which he has thought, or in the form in which he develops his matter — that is to say, what he has thought about it."
January 1, 1970
https://en.wikiquote.org/wiki/Arthur_Schopenhauer