Since You've Been Gone by Morgan Matson
I thought of a bucket list without the death as I was reading this book. Sloane has disappeared for
the summer, without telling Emily where she went or when she is coming back. Emily is devastated, all their summer plans hinged on the two of them being together and Emily doesn't really know how to be by herself. Sloane mails a list of things for Emily to accomplish over the summer. Things that push her boundaries, things that make her look at herself and who she really is. Things that make her question her willingness to stay in Sloane's shadow, envying Sloane's easy confidence, independence, and seeming effortlessness. Of course, things aren't always the way they seem; and Emily makes new friends, learns to see outside of herself and Sloane's bubble, her world expands.
I've had girls already reading and recommending this one to each other enough that the hold list will carry over to next school year. I bought a kindle version for myself when it went on sale, so I wouldn't have to compete with the girls and could read along with one of them. We had fun as we discussed it together.