I don't think a book can be measured by language level.
The Lord of the Rings has only some old English words, elvish words and poems.
These are the most difficult language elements in this book.
There is also a more circuitous grammar with classical usage. Of course, the grammar is absolutely formal and authentic, and it is beautiful.
It's just sometimes difficult. ...
Don't worry too much. I suggest you buy one and read it. It would be best if you could understand it ~