Like many of his novels, J.R.R. Tolkien has employed a theme of Christ figures although the author does not literally state this or make an obvious connection. It helps having a background knowledge of Satan, God, and other Christian entities.

There is a theme of death pervasive in the text as men grapple with mortality and Elwing and Eerendil are able to thwart it.

The theme of pride is pretty common as well. Generally, pride is one of the main catalysts for a lot of the conflict in the novel. Melkor and Feanor are the two characters who exhibit this trait in excess. When Melkor attacks Valar and is woefully outnumbered, his pride masks his ability to think clearly and he incorrectly thinks that he is strong enough to attack on his own. When that doesn't work out, he of course begins to plot his revenge because he will not be defeated.

I would argue though, that because the book is an expanse of time in order to establish a history, that perseverance is a theme due to the breadth and information that these stories entail. When reading this particular work, it is very much more of a history in that we absorb the happenings and characters to further our understanding of The Lord of the Rings universe. In doing so, we see characters moving from story to story effortlessly. It reads almost like the Odyssey in the way there are many stories with a common goal.