The two most recently books I read did not end in ways I expected at all.
Gone Girl is about a couple going through a rough patch in their marriage (to say the least) when she disappears on their wedding anniversary. At first I thought it would be your typical whodunnit but I was way wrong. It was much more twisted and interesting than that. I wish I could tell you more but seriously any more and I would give away too many of the juice details. Just read it.
The Husband's Secret was a Nancy recommendation and since it takes place down under, I was sold. It tells the stories of three families and (as would be expected) they are eventually intertwined. But really that is the only very predictable part of the book. Most of the book goes along ho-hum. Interesting enough to keep you reading (there's the secret from the title, a love triangle, an affair...so plenty of reason to read). The last few chapters and then the epilogue, goodness the epilogue. Wowzas. Total curve ball.
I know I'm not giving you a lot on either of these but with the super unexpected endings I think I'd unintentionally give something away. And that would ruin them for you.
Take my word, they are both worth reading.