The whole point of reading the book is to enjoy ending.
Why would you spoil it? Unless you've decided not to finish said book, reading the ending is like checking the credit card statement in November so you don't have to wait for Christmas morning to find out your presents. Talk about ruining some of the best of life's moments. Sheesh.
Some of us disagree that the point of reading the book is to enjoy the ending! That's only one of the pleasures of reading.
I loved Octavian Nothing for the total immersion in a pre-revolutionary-war and revolutionary-war setting, for the beautiful language, for the anger bubbling under the surface, for its rigorous development of the themes of liberty and hypocrisy and the way we interpret our own history.
I loved Absolutely True Diary of a Part-Time Indian for its anger and its humor and the way they were woven together, and for its absolutely believable teen-boy voice.
I loved The Disreputable History of Frankie Landau-Banks for its incisive observations and commentary on our "post-feminist" society and the subtle ways it still manages to work against women having power; I also loved the pranks.
(It's a month before the election, I'm sorry, I'm coming up with all these political books!)
In a book where the plotting is really rigorous and twisty, and one of the book's great strengths, then I can see where it's a pity to spoil yourself. When Harry Potter 7 came out, I did my level best to stay away from all spoilers! Where there's a mystery at the center of a book, I can see where it's a pity to spoil yourself.
But... a novel is like a scavenger hunt through a beautiful city. You might be completely focused on finding a cheese shop that has a particular cheese, or a skein of bamboo yarn, or a shop that's been in business since before 1800 - you might be totally focused on finding the clues and getting the prizes - but the real POINT is for you to explore, to see things you'd never seen before, to go off the beaten path of Crate & Barrel and Barnes & Noble.
The novelist is trying to lead you through an exploration of character and setting and theme, and in some ways - this isn't true for every novel, but it's true for some - the narrative drive, the desire to find out what happens at the end, is just the bait. So I really don't think that a novel can be reduced to finding out what happens at the end.