“Authors write books for one, and only one, reason: because we like to torture people.”

Source: A Mathematical Theory of Systems Engineering (1967), p. v;

Variant: A bad book is as much of a labour to write as a good one; it comes as sincerely from the author's soul.
Source: Point Counter Point

Source: Illuminations: Essays and Reflections

Source: The Letters of Dorothy L. Sayers. Vol. 1, 1899-1936: The Making of a Detective Novelist

As quoted in C.S. Lewis (1963), by Roger Lancelyn Green, p. 9

Source: Epigrams, p. 353

J. K. Rowling, as quoted in ‪Harry Potter's Bookshelf : The Great Books Behind the Hogwarts Adventures‬ (2009) by John Granger <!-- also partly in Biography Today : Profiles of People of Interest to Young Readers Vol. 17, Issue 1 (2008), p. 142 -->
2000s
Context: I think most of us if you were asked to name a very evil regime would think of Nazi Germany. … I wanted Harry to leave our world and find exactly the same problems in the Wizarding world. So you have to the intent to impose a hierarchy, you have bigotry, and this notion of purity, which is a great fallacy, but it crops up all over the world. People like to think themselves superior and that if they can pride themselves on nothing else, they can pride themselves on perceived purity. … The Potter books in general are a prolonged argument for tolerance, a prolonged plea for an end to bigotry, and I think it's one of the reasons that some people don't like the books, but I think that it's a very healthy message to pass on to younger people that you should question authority and you should not assume that the establishment or the press tells you all of the truth.