Before I read this book, I looked for the spoiler. I wanted to know what the promise was. I had an idea, but I wanted to be certain going into it. No one posted spoilers in the handful of reviews I read. And now I know why. This book is AMAZING. It's thoughtful and heartbreaking and mother fucking phenomenal. And I won't post the spoiler here either. Because it is the main point of the plot and the motivation for every character in the book. I loved every single page of it.