I loved the book "The Girl You Left Behind" so when I saw it had a prequel I wanted to read it. I loved getting the backstory of Liv and David's marriage. I really identified with her in that she didn't feel valued or loved in the beginning of her marriage. It seems as if she, like most of us, was swept up in the romance of the marriage but was not prepared for the work and compromise that would be involved to keep it going.
I also liked learning the backstory of the painting and how it was a reflection of Sophie and Edouard's marriage at the time he painted it. I can understand now how much this painting meant to both them and Liv.
I would recommend reading this before "The Girl You Left Behind" as it will help you understand the motives of the characters better. I would highly recommend both of these books and I hope you enjoy them as much as I did.