It isn’t possible to overstate the impact this story has had on all kinds of media (books, films, video games, music etc) since it was first published in 1955. The world Tolkien writes about feels alive and full of history (in part because he spent years creating a complete overarching mythos and history of this world and the people in it (of which the Lord of the Rings is but a small part).
The depth of the book cannot be overstated. Everything has a backstory. Answers for questions are often sprinkled around in conversations spread throughout all the books. Tolkien spent years working on the Silmarillion before starting this which is why so much detail is sprinkled throughout.
And Tolkien was crazy detailed with everything. He plotted every step of the journey out on a map and ensured everything, including the phase of the moon, was kept consistent.