Bunny by mona awad. Less of a single moment of 'didn't see that coming' and more of an entire book worth of 'what is happening' penpal by dathan auerbach. That ending is like a punch in. Great ending, that i didn't see coming from a mile away. Legitimately the only movie that has ever left me with my mouth open in shock from the twist.
Jeffrey deavers is pretty good at plot twists, but after you've read a few of his books, you start trying to figure out what the twist will be because you know it's coming and that sort of spoils it.
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