Years ago I found The Lord of the Rings book from a flee market for a measly one euro price. Having watched the LOTR in a movie format, I thought it would be a good read. Later on I went ahead and read the Silmarillion, which Tolkien thought of as his main work. He just never finished it, so his son, Christopher put it in a coherent format. It's basically a history book/mythology epos about the events of creation of the world to the birth of elves and humans and their doings and conflicts against the og bad guy, Melkor (aka. Morgoth) – whose chief luteunant Sauron started as – all before the events of The Lord of the Rings.
You learn about valar, the Mights who govern the creation of Eru Iluvatar (the God) who created the world and showed glimpses of it to valar through his symphony he played when nothing had materialized yet. The og bad guy Melkor, the most powerful vala, was an obnoxious dude though and created dissonance from the beginning to Eru's symphony. He wanted to create his own stuff from the beginning, and grew bitter when he couldn't, and started to corrupt everything that he could. He's kinda like the fallen angel Lucifer from the bible, and all the evil and corruption is of his origin in Middle-Earth and other lands.
The legendarium (the word that needed to be invented to describe Tolkien's work) is massive and detailed and it's fun to research the family trees and realize that Galadriel is Elrond's mother-in-law. Actually, Elrond's parent's are the distant ancestries of Aragorn. Aragorn is actually like 80 or so years in LOTR, because he has that elven blood that grants longer lifespand. Actually, an even further ancestor for both of them is a maia (lesser spirits who come after valar in their might, Sauron and Gandalf, for example, are maia). Through that there's some "divine spirit" from
Anyway, too much geeking here if you don't have any context of what I'm talking about. You'll have to google the names if you don't remember them from the movies, because I'm too lazy to craft anything fancy to this post.
It's crazy though how much reading this stuff fleshes out all the events in LOTR. Take the West, for example, where Frodo and the companions go at the end of the trilogy. That West is Aman, Undying Lands – where the kingdom of valar also lies – where lot of the events in early days took place. Or the fact that elves leave there from Middle-Earth: it's because of the Three Rings had restorative magical powers and Elrond and Galadriel could use them to create a realm in Middle-Earth where they could last. With the destruction of the One Ring though, the lesser rings also lost their powers. Elves, especially those who'd been to the West, had the need for incorruptibility and would grow weary and eventually wither away into spirits under the influence of a mortal world. Elves had been trickling for a long time back to the West, but now without the Three Rings, the last beacons of incorruptible realms would fade, thus it was time for the last of them to leave.
Silmarillion, this stuff is legendary, I like it.