Finished February 13
Maybe a Fox by Kathi Appelt and Alison McGhee
This children's novel is aimed at the 10-14 age group. 12-year-old Sylvie and 11-year-old Jules grow up at the edge of the forest, living with their dad after the mother died when Jules was just five. Their best friend is Sam, who lives nearby. Sam is 11 and a half. The two girls are close, and play a lot of games together include a game that imagines what happens when you die that they use to imagine whether their mother went with the wind, or became a star. Jules is a rock hound, always looking for interesting rocks. Sylvie is a runner, always trying to become faster, but without explaining why to her younger sister.
At the end of a path through the woods is a river. The river disappears into an underground cavern and reemerges beyond into a more placid pool before resuming its journey. The girls have been warned against going to the river at its more dangerous point, but are drawn by the stories associated with it, the promises of wishes fulfilled when wishing stones are dropped in.
Sam is glad that his older brother Elk has returned from Afghanistan, but his brother is different and seems to have left part of himself behind. Also left behind is his best friend Zeke, the son of another neighbour. Elk had asked Jules to look for the mysterious stone Grotto that legends spoke of, and leave two agates there for him and Zeke if they didn't return, and Jules still searches for this lost place.
When Sylvie goes out for a run one morning against her sister's wishes and doesn't return, the changes to Jules and her father's lives are massive. Meanwhile, nearby, a mother fox gives birth to three young cubs, knowing that one of them is different, tied to the spirit world in a way she recognizes but doesn't understand. The stories of the young fox Senna, and Jules are tied together along with other lost souls.
Another story of loss for children is Beautiful Goodbye by Nancy Runstedler.