Could you recommend any books for English learners.

I’m learning English and I’m thinking to start reading books in English. My level is in between intermediate and advanced. I’ve read just the first one of Harry Potter. When I read it, I found a lot of new words which were particularly used in writing I guess and I took so much time to finish it. I’d like you to recommend good books for me. Harry Potter level is the best I think. Less pages is better. Furthermore, best seller books would be nice. It’s hard to buy actual books from abroad in Japan. Sorry if I wrote the wrong way.

by pup1jan