Amazon Kindle & Fire discussion

Hi! I want to ask for help in finding a book that I read a long time ago. You may have read it, too.
The plot is that the husband before his death to his wife left 10-12 letters with tasks for her, so that his wife could let him go.
And for a certain period of time, she opened one email a month and completed the task.
If you have read this book, please remind me, in the last letter he left her an engagement ring ?
I can't remember the title of this book and I want to read it again, because I recently watched a movie based on this novel and I want to compare the differences between the film and the book.

This book is called PS I love you
And no, at the end of the book, he didn't give her an engagement ring . They were already married by the book.