Earlier quoted context omitted.
I occasionally think about the end of The Man in the High Castle, when the characters realize they are living in a fictional alternate history.
!!! SPOILER ALERT ABOVE !!! Hopefully you saw this before reading the above comment.
http://www.wired.com/2011/08/spoilers-dont-spoil-anything/
If a story isn't worth reading if you already know the ending, it's not worth reading without knowing the ending either. Good stories cannot be spoiled. Good stories are not merely puzzles to be savoured for a single punchline.
We also enjoy stories we already know well. It's why James Bond movies keep getting churned out despite all following the exact same formula or why Shakespeare plays are still in production centuries after they were written. Only bad stories are ruined by knowing the story.