I'm reading through the series for the 1st time, having already seen all the movies. This book was the first one that stood out to me as being far better than the movie. That is, they are all superior to their film versions, but this is the first where I felt like I had missed a great deal by not reading the book.
The climax and denouement of this book are the key transition in the series. It does an excellent job of transitioning from the lighter fears of the previous books to the darker menace of those to follow.