I don't read many books (I want to read more), but when I do I like something engaging, fun, imaginative, and different. So, I'll recommend any good fiction book that engages you. A book you can't put down. You want to keep reading to find out what happens next. It causes you to think, it causes you to imagine. It can cause you to think about things uniquely instead of being told to do so and give all sorts of ideas and new thoughts. If like me, you will end up remembering the characters, the situations for almost life and want to come back to re-read it some day.
My favorite modern day fiction books are fantasy / science fiction, something I would never experience in this world. In order: Shadows of the Empire by far my favorite, no reason off the top of my head and I am not a Star Wars fan, but I love it none the less. Followed by Harry Potter series. It's honestly a very fun read. Lord of the Rings and Hobbit will be popular choices I'm sure, but they just did not catch me and engage me like these 2.