The hero's journey in its most basic form, but that is definitely not to say it's not extremely satisfying to watch Bilbo grow over the course of what's just a really good adventure book. It goes without saying that Middle Earth is an insanely rich world - Tolkien was a right nerd, in the best way possible. Him and Thomas More have proved to be a lethally effective tag team in terms of coaxing my autistic ass into getting very invested indeed in linguistics, so if things continue on their current heading, I may end up having to credit this book for what I hope is a long career as a linguist. Point is, it's really good, and you should definitely give it a try, even if you don't intend to dive fully into this universe, and it's a great starting point if you do!