The best stories are the ones that are not predictable. The stories I love are the ones that have events or endings that are unexpected. I recently read a series that had me at the edge of my seat with anticipation of what would happen next. I couldn't see a thing coming. If you are interested, it was the Chaos Walking Trilogy by Patrick Ness.
I wish more books were written like this; it keeps things exciting. It makes it so you don't want to put the book down in fear of missing something. It shocks the mind to attention. It makes the reader want to read in great detail in hopes of catching what happens next.
Keep your stories unpredictable and you will find a more loyal readership and a more fascinating story.