The beginning is a brief retelling of the events of the show, mostly focusing on what John thinks of the whole thing, just to make sure no one's approaching the story with a conflicting headcanon. This is pretty important because the story conflicts even my headcanon, so I have to address those points of conflict. Then I can say "we all on the same page now? Good. On to the plot."

At the end... there is sadness, and ambiguity, and I have a clear picture but I can't tell you because spoilers. But if you watch Sherlock and read Paper Towns, you'll have a pretty good idea what happens in my story, I think.

Poor John.