I just finished Lock and Key! It was a very rewarding read, I practically just spent the last 3 hours reading it.
I enjoyed it, the book surprised me and was pretty touching. The plot wasn't too predictable, and I was sometimes surprised when the book tricked me.
I was very happy with the ending, though it took a little processing, and it almost seemed a little rushed.
If I could talk to Sarah Dessen, all I would say is slow down just a bit, a little more detail would have been nice in the ending. She must have been working with a deadline, because the ending didn't seem to compare to the rest of the book. It seemed like a 12 year old filled in the alternative ending.
I rate this at 4 star book, only because everything was so rushed.
But I would still recommend it, because every book has one bad thing about it.