There are no rules out there, but there are sins, and the cardinal sin is boredom. Robert McKee
Authority rests with the reader. They have total control over your story. They control when they start to read and when they stop. You cannot force them to do anything. This is their choice, and they exercise their authority when they put a book down.
Why did they stop reading? Possibly we grew enchanted with our powers of description and failed to keep the ball rolling. Characterisation, theme, mood; none of these stand for anything if the story is dull. If the story grabs the reader, all else can be forgiven.