The parts I most enjoyed about this book were the historical facts about Guernsey, and the footnotes, as Cersei mentioned. Otherwise, I found it a bit... meh. I didn't like the main character, and I also just find that books about a) teenagers who try and stay friends with bitches and b) teenagers who falsely accuse their teachers of sexual harassment are just not my sort of thing.
My take on the ending was that her father had killed himself and his mother covered it up, but was it murder? TBH I read most of it v quickly as I wasn't really enjoying it and just wanted to get it over with, so I may have missed out on some things! Am interested to hear that so many people on Amazon loved it, will have to go and have a look at those reviews...