Writers can learn a great deal from watching movies. This weekend we watched the second movie in The Hunger Games series. I admit I did not read the series and my comments are based only on the movie. I enjoyed the movie, but felt like it ended in the middle of the story. Many writers will tell you that each book in a series needs to have its own gratifying ending even if it is part of an overall story. If you don't believe this, watch the first two movies in The Hunger Games series and ask yourself how you feel at the end of the second movie. You do want to see the next movie in the series, but until it comes out, you are left feeling like you put a book down in the middle. Your audience may hang in for the next movie/book or they may be upset and feel like they wasted their money.
The owner of a bookstore once told me she has customers who won't read a series until the entire series is in print. They don't want to get caught up in something that makes them wait for another installment. By giving your audience a happy ending in each installment they walk away with a feeling of contentment that can carry them until the next book/movie comes out.
Experienced authors often say your career is only as good as the ending of your last book. That is what a reader remembers when they decide to purchase your book- or not.