Adam Gopnik cuts to the core of the author's influence on the fantasy genre:
[T]he fantasy readers’ learned habit of thinking historically is an acquisition as profound in its way as the old novelistic training in thinking about life as a series of moral lessons. Becoming an adult means learning a huge body of lore as much as it means learning to know right from wrong.
We mostly learn that lore in the form of conventions: how you hold the knife, where you put it, that John was the witty Beatle, Paul the winning one, that the North once fought the South. Learning in symbolic form that the past can be mastered is as important as learning in dramatic form that your choices resonate; being brought up to speed is as important as being brought up to grade. Fantasy fiction tells you that history is available, that the past counts. As the boring old professor [Tolkien] knew, the backstory is the biggest one of all. That’s why he was scribbling old words on the blackboard, if only for his eyes alone.