(Harry Potter to me is the ultimate example of fun and adventurous themes.)
The second reason is way more personal for me. I work in education and I mostly work with middle school students. I love my students and always want to help encourage students to read more but in order to do that, I need to be able to ensure that I have books to recommend to my students. Staying on top of YA and even chapter books for younger students is important to me. I don't want to suggest books that don't work for students; maybe it's not a subject they can relate to, maybe it's not a subject they like, maybe the reading level is too advanced for them, maybe the reading level isn't advanced enough.
It's also really rewarding to be able to talk about books with students. I am not a Language Arts teacher, so when I am talking about books with my students, it is normally in a more casual way and it is a great way to get to know my students and let them get to know me. It's one of my favorite parts of my day.