The story was predictable, but honestly that doesn't matter. It's a simple story but a powerful one. One of the morals of the story is to look for something "Kira-Kira", or "glittering" in everything. And that's a pretty great moral.
I don't have a sister, so I can't personally relate to Katie and Lynn's relationship, but I thought their bond was very sweet.
The main focus of the story is Katie and Lynn's relationship, but there are other things going on too, like the racism prevalent in the American South in the '50s, and unions for factory workers. I think this historical fiction book is perfect for kids, to introduce them to these topics in a gentle way.
Kira-Kira is a good book, and I recommend. Three stars.