Well, I am 40 years old and my favorite books are the Harry Potter and Fablehaven series' (I guess those might be considered kids books? Or are they young adults?). I like their creativity and imagination. While I like adult books too, I have a harder time finding ones that I like. I find too many seem to focus on sex or graphic violence. That said, my favorite "adult books" are Jane Eyre, The Guernsey Literary and Potato Peel Pie Society, and A Man Called Ove (though initially I found that one disturbing). But I find the first place I go when I enter a book store is the young adult section!