I really liked this book.  It is a message of hope, of hope for the future, and shows that it will be the younger generations that will lead the way.  The story is riveting, imaginative, and hopeful. I like how the author builds up the scenes as she is going along, rather than trying to give you the whole "concept" in the first few pages.  It sets up the entire story, but lets the story tell itself over the chapters, which is nice because you are not trying to remember every detail from the beginning of the book.  Over all, the friendship of Riv and Dan is what sets up this story to be exceptional.  It's the life long concept of sharing burdens, as in the song "Lean on me" by Bill Withers.  Afterall, life's travels do seem to be better when we share both the burdens and the joys with friends.