J.R.R. Tolkien's The Lord of the Rings is a well-known intellectual property to literary and film audiences alike. But for a long time it was fairly niche and specific to "nerd culture" and fantasy enthusiasts. Tolkien built a world so expansive that he included a series of appendices at the end of his novel further explaining the mythology Middle-earth. Originally, he had even intended for all three books to be published as one volume. However, his publishers advised against this fearing the public would be overwhelmed by such a hefty book.
Source：https://www.cbr.com/silmarillion-worth-reading-lord-of-rings/
