Much emphasis has rightly been given to hooking the reader in the first chapter. With so many choices, it has been said that you have 30 seconds to get readers emotionally involved with the characters and the story.
However, do not underestimate the importance of the final chapter for, selling the next book is it’s job. How does it accomplish that? By leaving the reader completely satisfied, moved. Think back to a book which, when you read the last page, affected you deeply. I remember wanting to go back and start again. Then going out to see what else the author has written. That is resonance.
How do you create this kind of ending? Take out your favourite books, the one which affected you most deeply. Read the ending again, taking careful note of what you feel. Then read it again, this time taking note of how that feeling was created. What was it about the writing that affected you so much? Practice ways to evoke that same feeling from your readers.