R for resolution.  Another one of The Big 5 (story essentials) and for good reason.  This is where all the questions you've planted in the reader's mind get answered.  Conflicts are decided, choices are made, treasures are found, and so on.  You've brought the reader on this long journey and now they find out if the trip was worth their time.  So, you've got to have an ending (resolution) that lives up to the story.  A destination worth the long ride in the hot car with the complaining kids and the smelly dog. 

Have you ever listened to someone tell a long and tedious joke which led to a weak punch line?  You probably shook your head and admonished yourself for wasting your time.  Story resolution can have that same effect on the reader.  As I was reading the Harry Potter series I couldn't help but wonder how the author would bring the epic story to an end.  Well...she didn't disappoint.  I've gone back and read the final chapters of the last book dozens of times.  It was that good (I'll spare you my disappointment with the movie version), and I can't imagine how she could have brought the saga to an end any better.  In other words, the journey that spanned years was totally worth it.

Some authors resolve the story with an unexpected twist.  You think everything is over but wham...he hits you with something you never saw coming.  She reveals something you never considered.  Misdirection is a superb story element that rears its ugly head in the resolution.  It leaves the reader thinking about the story long after the book has been shelved or passed on.  Your story sets it up, your resolution brings it home...and...has the reader buying your next book.