I wrote a longer draft about the Tolkien biography I finished reading recently, Daniel Grotta's J. R. R. Tolkien: Architect of Middle-Earth (1978 ed.), but this excerpt is what I will share:
Here's a quote from Tolkien that surprised me (p. 105):
"If you really come down to any really large story that interests people and holds their attention for a considerable time, it is practically always a human story, and it is practically [always] about one thing all the time: death. The inevitability of death. Simone de Beauvoir once said that there is no such thing as a 'natural' death. Nothing that ever happens to man is ever natural. And his presence calls the whole world into question. All men must die, but for every man his death is an accident, and even if he knows it ... an unjustifiable violation. You may agree with these words or not, but those are the keyspring of The Lord of the Rings
I would have guessed that the Lord of the Rings had nothing to do with death. Some characters die -- but characters must always die. I wouldn't guess most of the youthful fans of Tolkien found LOTR to be so existential. If I had guessed, before reading the quote, as to what LOTR is about, it is about how a story can get into you and take you somewhere else -- as though everything is a story.
Another surprising quote from Tolkien (p. 123):
"I know that one interviewer explained it: It is written by a man who has never reached puberty and knows nothing about women but as a schoolboy, and all the good characters come home like happy boys, safe from the war. I thought it was very rude -- so far as I know, the man is childless -- writing about a man surrounded by children, wife, daughter, granddaughter. Still, that's equally untrue, isn't it, because it isn't a happy story. One friend of mine said he only read it at Lent because it was so hard and bitter."
This reminds me of criticisms of the Book of Job's framing story. "How cheap! He gets it all back in the end." But Job never gets his first set of children back. The Bible can be dry and sort of laconic, you can miss the details. Similarly, it seems, with The Lord of the Rings. Somehow Tolkien and at least one person he knew (maybe someone closer to his generation?) saw the death in a fairy story, and we are the ones who can't see it.