Harry Potter and the Goblet of Fire (Book 4)
What I loved in JK Rowling by this time in the series was her whimsy and her world building, and this is no exception. Every book introduced new characters, new aspects to the magical world and this book was a turning point in so many ways. For one, this one turned the world dark. It was the first time the trio of Harry, Hermione and Ron don't triumph wholly against evil, where there are costs, and where we get a hint doing the right thing won't always be easy or without terrible sacrifices.
