My Sister's Keeper was the first Picoult book I read, and it'll be my last. I couldn't stand the ending; I'm siding with those who say it's Deus Ex, definitely.
SPOILERS FOR MSK
Sure, the story ended up being more about the big sister's right to choose her own course of treatment (or, er, to opt out of treatment entirely) than the little sister's right to bodily autonomy, but here's the thing. The book raised a lot of questions about the morality of basically having and raising a child to farm out their body tissues for your older, sick kid- and a lot of the book *was* based around the idea that this younger child was her own person, and that it was important to consider her interests as well as her sister's. By randomly killing this younger sibling off at the very end, she's again reduced to nothing more than a bunch of organs and bone marrow, etc, for the harvest.
And also, the big sister now faces significant pressure, I'd think, to choose to take those available tissues. For one thing, if she dies too, then her parents will have double the grief; she's got to be thinking of that. If she gives up now, her little sister will have died for nothing, or at least, that's how some people are going to look at it. Plus, there's no point in worrying over any further harm to her little sister from invasive and painful procedures, right?
So yeah. Her little sister no longer matters as a human being- despite all the fuss the book made about that issue- and that choice the big sister wanted to make for herself, which was the whole point of the book? Is she really going to make any other decision, given what happened at the end? That ending totally negates the entire book, for me. It's like Picoult got to that point, couldn't decide upon which choice the big sister would actually make, and decided to just take the whole matter out of her hands. OHHH it made me so mad, I'm still ranting. LOL