What advice do you have for fantasy novelists?

Believe. In his Introduction to Shakespeare, poet and critic Samuel Taylor Coleridge talked about "suspension of disbelief." You've probably heard that term before, and it's the idea that somebody watching a play or reading a book can "forget" their mundane situation long enough to sort-of pretend that the play or book is real.

But Tolkien said that fantasy writers don't just create suspension of disbelief, they create something even more powerful and amazing; they create belief. I think a fantasy writer has to immerse herself in her world, to believe in it so completely that she can convey the reality of that imagined world to her reader. When a reader engages with a thoroughly "believed" world, she can transcend reality, and comes back to our world changed. I'm totally with Tolkien that fantasy novels can change the world.