Quick summary for folks who don't know much about it: Lord of the Rings (together with its prequel, The Hobbit) is a 3-volume fantasy novel written by a professional linguist that more or less defined our modern concept of the genre. Many, many tropes that are a staple of medieval-fantasy works either originated with or were popularized by Tolkien - "halflings" as a concept are pretty much taken wholesale from his works.
Re-read LotR for the first time in a lifetime earlier this year. The Peter Jackson movies were a big thing for me and my sisters growing up (we'd go to the cinema to watch them together, then spend the following Christmas and Boxing Day going through the DVD box set extras), and one of them gave me the book as a present shortly after the final film had come out. It's by no means a perfect piece of literature, but the sheer love and depth that Tolkien threw into his world is palpable on dang near every page. The tale just draws you in, and I had forgotten how strong that pull was until I started reading the tome again.
I've owned a copy of Unfinished Tales for years but never read it, and I pulled it out again after I finished LotR. Still sitting there where I placed it to wait for its turn. Really ought to get around to it.