Growing up during the Dust Bowl, Jack and his sisters know little but poverty, depression, and anxiety. Their father is depressed, the older girl is seriously ill, and Jack is badly bullied by other boys. The children's only pleasures are fantasy stories and their mother's memories of a green and prosperous past.
The dominant use of dull, sere colors and the repetitive, often wordless panels did a great job of conveying the dead dryness of the land and the boredom and despair of the people who could do nothing to save their livelihoods. This technique did make the book a little dull, especially visually, but it would be effective for teaching about the Dust Bowl.
I'm not particularly interested in this period and was attracted by the supernatural element. I wish that had been developed more extensively.