Apart from the Beatles references Penny used sometimes, the book is not that Beatles-ish. The lessons you learn rather from Diane than from Penny. I think Diane is the one that really makes a big step in her life and grows into independence and womanhood. In the end, all of them learn a lot, but her development reminded me of something important (you have to believe in yourself and be someone you like) and I appreciated the kind reminder :P Girl power, juhui!! 
 But how on Earth could Penny resist Ryan for soooo long?? He's adorable, for God's sake!! xDDD