The Most Important Line From the Chapter

I'm finally making progress through my book Harry Potter and the Prisoner of Azkaban by JK Rowling. And I've started to notice a trend at the end of each chapter which also happens to be one of the most important sentences in that particular chapter. This sentence is somewhat of a conclusion sentence that sums up the last chapter while bringing us to the next chapter. I think these sentences are the most important because you can't just end a chapter with a normal sentence. You have to end it with a sentence that makes you want to keep reading and keeps you compelled within the book, wondering, pondering, questioning what's going to happen next so you don't have a choice to keep reading.

One example of these sentences is, ""I'm not going to be murdered," Harry said out loud. "That's the spirit, dear," said his mirror sleepily."(pg. 68) This sentence forces us to keep reading because we are so engulfed in the story that we need to know 'What will happen to Harry?' and 'Who is he seeing in his mirror?' Rowling does a fantastic job of leaving us on a cliffhanger at the end of each and every chapter and keeping us  wondering what will happen next.
Information and background knowledge one the book.