This book is for children ages 9 and up, and it also appeals to adults as did the Laura Ingalls Wilder and Harry Potter stories. The kids from the previous book, The Cave of Healing, arrive at Mammoth Cave and are soon confronted with big problems. Because these kids can magically reduce their size to even an inch tall, they become the heroes of the Cave's search and rescue operations. The author was assisted by Mammoth cave explorers and the Cave staff in getting the geology, geography, speleology, and hydrology of the Cave right, as well as authentic actions of cave guides and rescue teams. Roger Brucker, one of the most famous cave explorers in the world, said, "This is a gripping tale, full of fun and adventure." Midwest Book Review calls it "An engrossing story to delight readers of all ages."