In the seventh book, Zoey and Sassafras are excited to enjoy their summer with their magical friends. But . . . why is everyone so grumpy? A bunch of bad days one after the other lead Zoey to suspect that something more is afoot. It's up to Zoey and Sassafras to solve the mystery before they end up with one bummer of a summer

Each story in the Zoey and Sassafras series features a new magical animal with a problem that must be solved using science. There isn't a set formula for each book; Zoey sometimes needs to run experiments, while other times she needs to investigate a mystery, and yet other times she needs to do research. Zoey models how to keep a science journal through her handwritten entries in each story. Each story is complete with a glossary of the kid-friendly definitions for scientific terms used. The series highlights child-led inquiry science and the topics covered align with both Common Core and Next Generation Science Standards.