I thought this book was good, but, like you, I cannot classify it as the best book I read last year. Not even close. It does some really interesting things with friendship, and I loved a lot about the first half of the story, but you are right about the characters. Although not perfect by any means, I think Sam gets treated very poorly by Sadie for reasons that are more in Sadie's mind than legitimate. Thus, Sadie is probably the most unlikable of the main characters (aside from Dov, of course).

As I said, it's a good book, and I enjoyed it, but I am a bit perplexed about the gushing it elicited from so many people.