My Collection of Harry Potter's Book

This is the picture of my collection of Harry Potter's Book from the first to the seventh book. My future planning now is to buy the United States version of cover book for all set. Why? Because there are interesting illustration in the beginning of every chapter. It's okay to have 14 of Harry Potter books but I'm not sure if the sixth and the seventh book already have the US version of cover or not. Will checked in the book store when I have free time.