Harry Potter and the Goblet of Fire

One of the absolute greats

This book isn't just the best in the series, it's one of the greatest books of all time. The amount of action, the amount of content that's in this book is simply incredible. Without giving away too many spoilers, this book takes the series into a much darker, more serious area whilst making you fall more in love with the characters and giving them even more personality than before. It's truly sensational and is most certainly up there as one of my favourite books of all time.