Speaking on the evolution of Arthurian legend to include Galahad, the Round Table, a more interesting Merlin, etc:
It is occasionally forgotten, or seems to be, in the great scholarly discussions, that anyone who is writing a poem or a romance is primarily writing a poem or a romance. He will, of course, be affected, as the Crusaders in their task were affected, by all sorts of other things – his religious views, his political views, his need of money, the necessity for haste, the instructions of a patron, carelessness, forgetfulness, foolishness. But he is primarily concerned with making a satisfactory book. He may borrow anything from anywhere – if he thinks it makes a better book. He may leave out anything from anywhere – if he thinks it makes a better book. And this (it can hardly be doubted), rather than anything else, was the first cause of the invention of the glorious and sacred figure of Galahad.
-Charles Williams, The Figure of Arthur, p.62
This is another thing you can put in the “captain obvious” file, but it’s worth bringing up. His point is that this is forgotten in some SCHOLARLY discussions. It’s also why a person you share nothing with politically, religiously, or socially can still write a book that you recognize as outstanding. If they’re intention was excellent literature, they will do whatever they need to craft it well. However, if they’re primary intention was to preach (be it about global warming or eschatology), they may easily end up writing garbage. Even if the agenda is something you favor, it doesn’t make the literature any better.