People more familiar with Tolkien’s works probably already know that he was, famously, a philologist and linguist. The languages in the books and films aren’t just a collection of random sounds, they have a vocabulary and grammar, like any real language. In fact, some argue that he invented Middle-Earth to give his languages a home.
The languages of the elves, Quenya and Sindarin (not “Elvish,” as some might call them) have distinct grammatical structures and even influence each other the way real languages do. The etymologies and “older forms” of Sindarin can be found in Quenya, for example, as he loved to construct the entire history of a language.
Not only did he make languages, he even constructed an alphabet for them, just to make modern learners' lives a little more “interesting.” Called the Tengwar script, it’s the most commonly known writing system seen in the “Lord of the Rings” films. It uses diacritic marks to represent vowels. Examples of the text can be seen on the Durin’s Doors (made by Elves, if you were wondering), and the one ring, among others.
Tolkien was just as concerned about “real” mythology as his own epics. He is one of the main contributors to our current understanding of Beowulf, as he was one of the first linguists to treat it like a poem, not a fictionalized, historical record (the presence of dragons could have been a useful clue.)
While some say Middle-Earth came about as Tolkien’s attempt to “place” his beloved languages, the truth is not so simple. “The Hobbit,” for example, started out a bedtime story he would tell his children. Only later, would he place this story and some of its characters in his wider world. Fans should note that Quenya hardly shows up in “The Lord of the Rings,” while it’s more visible in his later works.
Owners of the books will also be aware that he left significant information about the world, timeline, and languages in the appendices of all three books. The whole trilogy took around a decade to complete. At first, it would have followed the tone of “The Hobbit,” but Tolkien quickly found that a darker, more serious tone was better.
The reasons for this vary, but an often overlooked one is the simple fact that his children, the original audience for “The Hobbit'' had grown up and were likely simply not as interested in explicitly a children's tale. And as Tolkien developed the nature of the one ring, it would be hard to keep up a child-like tone.
Originally, all three books were written as one, long narrative, but the publishers thought it best to split it up, mostly to offset the risks of a massively expensive printing process before the popularity of the piece was assured. During the time between publication, Tolkien did make a few revisions to “The Return of the King” and included more information in its appendices.