This book is something beyond the expectations, like one moment you think that everything is sorted and it's the happy ending and then the main ending came that wasn't much happy, the ending that still has some secrets with it.
The letter part leaves a question whether she actually did that or it's all just a writing.
I wasn't expecting it to be this much good and it deserves like 10 stars out of five.
Conclusion : if you can handle suspense and thrills that can make you want to just skip to the end but you still somehow keep control on yourself, then this one is surely for you