The Other Hand by Chris Cleave

We don't want to tell you what happens in this book. It is a truly special story and we don't want to spoil it.
Nevertheless, you need to know enough to buy it so we will just say this:
This is the story of two women.
Their lives collide one fateful day, and one of them has to make a terrible choice.
Two years later, they meet again - the story starts there...
Once you have read it, you'll want to tell your friends about it. When you do, please don't tell them what happens either. The magic is in how it unfolds.