I've started this review, scratched it, thought about it, re-started...
It's a difficult review for me because I felt so strongly about the mediocrity of the book. It's definitely not bad. It's not badly written, it's not badly plotted, it's not badly character driven... but it's not good either. I was very disappointed only because what I had read going in led me to believe this would be something special. I was very excited to be picked for this book, but unfortunately the excitement ended then.
What's good: the book is a very quick read, and there are characters or moments where you really care. The mystery-aspect of the book is intriguing and I definitely needed to know "what next." It was easy to read the prose, and I flew through the pages quickly.
What's not: the book is altogether unconvincing. It is unconvincing as a history novel, it is unconvincing as a love story, and it is unconvincing as a tale about the bonds of family. The book is written in letters primarily between "Sue" and Davey and between Margaret and Mother. The "voices" of each of the characters, however, were not distinct from each other (or, not enough to matter). The only way you got a sense of things was in the narrators' description of someone else -- i.e., I didn't learn as much about _____'s personality from their OWN letter as I did from a letter by someone else writing about _____. It was only by descriptions of others that personalities emerged.
Also, the letters employed overly-obvious and unrealistic conversation -- i.e., if my sister were to call me and I said "oh! hello big sister who lives in Chicago! It's so nice to hear from you again after just a week!" No one talks like that. There were several moments like that in the book, where there was over-explanation and no subtlety.
Additionally, the complete lack of self-awareness of ALL of the writers, combined with the complete obliviousness of each of the characters was infuriating and not particularly believable. Perhaps a character or two in a situation would have that complete lack of self-awareness or awareness of others... but every single character? Oh, of course with the exception of the all-wise grandmother/mother or the good-for-nuthin' brother, who play disappointingly minor roles.
What I disliked the most, however, is something that probably won't bother as many people as it did me. [SPOILER (highlight)]
All in all... it was disappointing, but it had a bit of intrigue. As I said, there were aspects of the book that I cared about; it was a quick read; there were minor portions of the familial relationships that were interesting; and it was not a flop.
So, THREE of five stars. Recommended for people who particularly enjoy long-distance romances and historical romances.