This rating is for the entire series until I get a chance to reread it and go book-by-book. All I can say is, I remember when I first got into this series at 13--despite being for 5th grade readers, I loved it! It was fun, suspenseful, and just plain weird. My collection is a mix of small softcover, larger softcover, and hardcover because I couldn't wait to get it all in one format. Whatever the bookstore had at the time I needed the next one, that's the one I bought!