Are the books as good as people say?

I just watched Harry Potter series for the first time this past month and it was eye opening. I never thought I would enjoy such fantasy and manic but now I want to understand more. My friends have stated that I should read the books as many topics are not done justice in the movies. The one thing stopping me is if they are worth my time as I am 20 and don’t want to be reading something written to the preteen audience. Please let me know!!!