Tolkien and J.K Rowling literature is pretty simple
Try reading teen-oriented thrillers/detective dramas too, that should do the trick.
The Hobbit definitely, but not the Lord of the Rings or the Silmarillion. Have you even read them?
I remember the first time I read LOTR in english. I learned a lot of new words that I haven't seen that often since.
Definitely not easy.
OP, what's your mother language?