"Cave of Old Ninety-Nine" by Elizabeth Gray is an exciting novel that tells the story of a group of friends who go in search of a mysterious cave in which, according to legend, an incredible treasure is hidden. They will face many challenges, dangers and secrets that this mysterious shelter hides. The author has successfully combined tension, adventure and friendship in an exciting story that will leave readers on the edge of their emotions and contribute to a deeper understanding of the values of friendship and loyalty. "Cave of Old Ninety-Nine" is a book that will not leave indifferent any lover of adventure literature.