Should I read the books?

So I've seen the movies several times, and I was wondering if it is worth reading the books? Does it add anything more? I mean, when I read the Game of Thrones books, it made the show look like absolute rubbish. So was wondering if there books were worth reading aswell?

EDIT: Thank you so much everyone for explaing what the books add so we'll, it's 3 in the morning and I can't wait to go to the bookstore when it opens. Literally couldn't sleep cos I am so excited, haven't felt like this since I was a kid 😆

UPDATE: So literally just the first chapter in and already seeing so much you don't see in the movies, like the professor's care for Harry from the beginning. Thanks so much for telling me to read it, it's awesome!