I read this story something like 10 years ago (I think it was fairly new around then), so I don't remember it too well, but the basic gist of the plot was this:
- The kid isn't very personable or motivated, I think he gets bullied in the first chapter
- He had a twin brother that died in the womb (a vanishing twin) (they talked about finding his teeth and hair at birth)
- The parents are scientists, I think? They make an artificial body and somehow get his brother's artificial intelligence inside of it
- They swap the twins bodies, so that the MC is in the artificial body and the twin is in his body
And that's how the book ends, I believe. It was horrifying as a kid for it to end on such a sad cliffhanger so I want to see if it had a sequel.