Looking for a book to broaden my vocabulary(English)

I mainly listen to audiobooks. And I find that when I take the time to listen to a book. Over the next weeks my vocabulary is broader and my sentence structure is more verbose. However recently I’ve struggled to find new books that catch my interest. I love games like DnD, Warhammer, LOTR. Mystical type stories. I also like sci-fi. What I stay away from is horror or thriller type because I don’t like getting anxious. Any other genre with a sci-fi setting I love. Any recommendations?