I had a really hard time concentrating on this book. The narrator was just a little too low key to keep my attention for extended periods of time, and the story itself is predictable as hell. I played a casual game once with more or less this exact same plot, and I'm sure I've seen a made-for-tv movie or two with similar story devices. The story goes exactly where you expect it to go from start to finish. I also didn't care much for Adrienne. She's a free spirit and well-meaning and all she touches eventually turns to gold, but I couldn't get over her invasive snoopiness that was essential to the character and the driving force of the story. I don't like busy bodies, sorry!
I did however really love William and Sarah. They were spunky and hopeful and sweet. I got all the good grandparent feels whenever they were "on page". They were the reason I kept going because I wanted to get to their HEA. I couldn't really get into the William/Gracie backstory in the letters because I was expecting the plot twist, but I did really like the letter that told how William was saved by Samuel in the foxhole. Makes me want to watch Band of Brothers again.
Will was kind of a hard ass and I've already spoken about Adrienne, so I couldn't really care about their goings on too much - though I tended to be on Will's side during their arguments, and of course everything worked out in the end.