Vicky, 14, is having a bit of an identity crisis; she isn't who she's always been (gangly and angular and plain) and she isn't sure she fits into her family or her church (or faith in general); her family is moving to NYC for a year; her Mother's best friend (they call her Aunt) is marrying her favorite Uncle and they're moving to California taking their ward (who has been living with Vicky's family). Changes, changes, changes that Vicky isn't prepared to deal with. We find that she's questioning God: His existence, goodness, general character.
Her parents (not as featured in this second book as in the first) have decided to take the family on a camping drive across the country to see the newlyweds in their new home; to give some space before the move to New York; and maybe just to give Vicky a different view of the world and get her out of herself.
The family makes a grand circuit driving from New England through Pennsylvania, to Tennessee, through the desert. In California is the high point of the crisis, but it isn't resolved for a long time ... they drive through part of Canada and Yellowstone, etc. before returning to New England. This is a circular route and the story is somewhat circular, too. There is a structure where they're meeting the same people or facing the same struggles at similar points to the story. Hm. On one of their first camps they meet Zachary Grey and his parents. On one of their last camps (at least in the story) they meet Zachary and his parents (the parents they haven't seen since the first meeting).
At that last camp, there is a crisis and Vicky rails against God ... through the 121st Psalm. The book's title is here, "The sun shall not strike you by day, nor the moon by night." (Ps 121: 6) This is the high point of Vicky's crisis of faith that has been building through the whole book.
... "Do it MY way, God, not YOUR way, MY way."
Sometimes He picks most peculiar ways.
I looked up at the sky and at the stars and at the moon, and the moon was no longer smiting me. I didn't know why. I didn't know what the difference was. ...
The point was that now I knew it didn't matter whether or not I understood. It didn't matter because even if I didn't understand, there was something there to be understood.
This is a book about finding oneself. And that finding oneself can only been done in relation to God. In relation to Christ.